|
|
| |
145 records found
1.
Gäumann, M., S. Henry, et al. (1999). "Epitaxial laser metal
forming: analysis of microstructure formation." Materials Science and
Engineering A 271: 232-241.
Epitaxial laser metal forming (E-LMF) is presented as a new cladding
technique which combines the advantage of near-net- shape manufacturing with
a close control of the solidification microstructure. E-LMF is a process
where metal powder is injected into a molten pool formed by controlled laser
heating. Laser surface treatment has the advantage that heat input is very
localised, thus leading to large temperature gradients. This is used, in
unison with closely controlled solidification velocities, to stabilise the
columnar dendritic growth, thereby avoiding nucleation and growth of
equiaxed grains in the laser clad. It is possible with this technique to
deposit a single crystal clad by epitaxial growth onto a single crystal
substrate. In this paper, the microstructure obtained by E-LMF is analysed
by scanning electron microscopy (SEM), optical microscopy (OM) and indexing
electron backscattered diffraction (EBSD) patterns. In particular, the grain
structure formation in the deposit during the process and the influence of a
subsequent heat treatment on precipitation and recrystallisation is
characterised.
2.
Gaffard, V., A. F. Gourgues-Lorenzon, et al. (2005). "High temperature
creep flow and damage properties of 9Cr1MoNbV steels: Base metal and
weldment." Nuclear Engineering and Design 235:
2547-2562.
High temperature creep flow and damage properties of 9Cr1MoNbV steel and
weldment are investigated in the present study. First, an experimental
database is built to compare both creep flow and damage properties of the
base metal and the weldment. Metallurgical investigations before and after
creep tests revealed that the microstructural state is responsible for the
lower creep strength in the weldment. A simple analysis based on the
description of the steady-state creep stage and on use of empirical lifetime
prediction relationships is performed. It allows to predict the weldment
creep lifetime without performing an extensive number of
experiments.
3.
Gan, Y. X., J. W. Kysar, et al. (2006). "Cylindrical void in a
rigid-ideally plastic single crystal II: Experiments and simulations."
International Journal of Plasticity 22(1): 39-72.
Experimental results and finite element simulations of plastic deformation
around a cylindrical void in single crystals are presented to compare with
the analytical solutions in a companion paper: Cylindrical void in a
rigid-ideally plastic single crystal: Anisotropic slip line theory solution
for face-centered cubic crystals. In the first part of the present paper,
the theoretical predictions of the stress and deformation field around a
cylindrical void in face-centered cubic (FCC) single crystals are briefly
reviewed. Secondly, electron backscatter diffraction results are presented
to show the lattice rotation discontinuities at boundaries between regions
of single slip around the void as predicted in the companion paper. In the
third part of the paper, the finite element method has been employed to
simulate the anisotropic plastic deformation behavior of FCC single crystals
which contain cylindrical voids under plane strain condition. The results of
the simulation are in good agreement with the prediction by the anisotropic
slip line theory. Material: aluminum.
4.
Gan, Y., D. Lee, et al. (2005). "Structure and properties of
electrocodeposited Cu-Al2O3 nanocomposite thin
films." Journal of Engineering Materials and Technology 127(4):
451-456.
Nanocomposite thin films which consist of 50 nm
Al2O3nanoparticles in a copper metal matrix were
deposited on a silicon wafer. The thickness of the nanocomposite thin films
was about 3 microns and the volume density of the nanoparticles was between
3% and 5%. The films were synthesized using electrocodeposition. The grain
size of the nanocomposite film was significantly smaller than the grain size
of control films of pure copper. Electron backscatter diffraction (EBSD)
experiments indicate that neither the nanocomposite thin films nor the
control films exhibits a crystallographic texture. Nanoindentation
experiments show that the hardness of the nanocomposite thin film is
approximately 25% higher than the hardness of the control films of pure
copper. A prototype of a microchannel array in the nanocomposite thin film
was made using standard microelectromechanical (MEMS) fabrication
technology. It is expected that the enhanced mechanical properties exhibited
by nanocomposite thin films have the potential to improve the reliability of
various MEMS devices which rely on thin metal films. The results presented
herein lay the groundwork for future studies in which the size, volume
density, morphology, distribution as well as type of nanoparticle in the
nanocomposite will be systematically and independently varied in order to
optimize mechanical properties.
5.
Gandin, C.-A., M. Rappaz, et al. (1995). "Grain Texture Evolution
during the Columnar Growth of Dendritic Alloys." Metallurgical and
Materials Transactions A 26(June): 1543-1551.
6.
Gao, J. S., H. Nakashima, et al. (1999). "Effect of Substrate Bias on
Si Epitaxial-Growth Using Sputtering-Type Electron-Cyclotron-Resonance (ECR)
Plasma." Japanese Journal of Applied Physics Part 2 38(11B):
L1293-L1295.
7.
Gao, J. S., H. Nakashima, et al. (1999). "Growth of Epitaxial Silicon
Film at Low-Temperature by Using Sputtering-Type
Electron-Cyclotron-Resonance Plasma." Japanese Journal of Applied
Physics Part 2 38(3A): L220-L222.
8.
Gao, J. S., H. Nakashima, et al. (2000). "Optimum Discharge Condition
of DC Bias Electron-Cyclotron-Resonance Plasma Sputtering for High-Quality
Si Epitaxial-Growth." Japanese Journal of Applied Physics Part 1
39(5A): 2834-2838.
9.
Gao, J. S., J. L. Wang, et al. (2000). "Study of the Effects of
Discharge Conditions and Substrate-Temperature on Si Epitaxial Deposition
Using Sputtering-Type Electron-Cyclotron- Resonance Plasma." Journal of
Vacuum Science and Technology A 18(3): 873-878.
10.
Gao, L. and K. C. Chan (1995). "The Grain-Size and Strain Dependence of
the Flow Stress of Polycrystalline Iron." Philosophical Magazine
Letters 71(6): 313-317.
11.
Gao, M., M. Mihalkovic, et al. (2004). "Phase equilibria and
thermodynamics of Ca-based metalic glasses." JOM 56(11): 187.
The CALPHAD method has become a powerful tool in thermodynamic modeling of
multi-component systems. However, when there is little literature
information available, critical experiments are needed to validate the
CALPHAD modeling. This is the case for the Al-Ca-Cu ternary phase diagram
(especially on the Ca-rich side). Research in this system originates from
the recent discovery, at the University of Virginia, that an unusually broad
glass formation range (GFR) has been identified near the Ca-rich side that
includes several bulk glass chemistries. This is in contrast to the narrow
GFR reported earlier with much poorer glass forming ability on the Al-rich
side. The GFR determined using melt-spinning and die-casting techniques, and
its structural and thermal stability was studied using XRD and DSC. The
solid-state phase equilibria were investigated using XRD, SEM, EBSD and TEM,
while DTA was used to characterize the solidus and liquidus temperatures. In
order to assist this study, first-principles calculations were performed on
this system and have proven to be important in prediction of phase diagrams
(e.g., solubility range) and minimizing experimental uncertainty, including
phase chemistry and structure. In this talk, details on integration of these
calculations with experiments and modeling will be emphasized. The
application of such self-consistent accurate thermodynamic descriptions to
explain the observed glass formation will be discussed.
12.
Gao, N., M. J. Starink, et al. (2005). "Microstructural evolution in a
spray-cast aluminum alloy during equal-channel angular pressing."
303-307.
A spray-cast Al-7034 alloy was processed by equal-channel angular
pressing (ECAP) to a total of eight passes at 473 K and the pressed samples
were examined using transmission electron microscopy, differential scanning
calorimetry and electron back-scatter diffraction. It is shown that the
grain size of the alloy is reduced to 0.3 μm by ECAP and the high
pressures associated with ECAP lead to a fragmentation of the rod-like
η-phase. The high temperature of ECAP also produces a precipitation of
η-phase. There is an increase in the fraction of high-angle boundaries
during the initial passes of ECAP but the fraction of low-angle boundaries
remains high even after eight passes.
13.
Gao, N., M. J. Starink, et al. (2005). "Microstructure and
precipitation in Al-Li-Cu-Mg-(Mn,Zr) alloys." Materials Science and
Technology 21(9): 1010-1018.
Hot rolled Al-6Li-1Cu-1Mg-0.2Mn (at.-%) (Al-1.6Li-2.2Cu-0.9Mg-0.4Mn, wt-%)
and Al-6Li-1Cu-1Mg-0.03Zr (at.-%) (Al-1.6Li-2.3Cu-1Mg-0.1Zr, wt-%) alloys
developed for age forming were studied by tensile testing, electron
backscatter diffraction (EBSD), three-dimensional atom probe (3DAP),
transmission electron microscopy (TEM) and differential scanning calorimetry
(DSC). For both alloys, DSC analysis shows that ageing at 150°C leads
initially to formation of zones/clusters, which are later gradually replaced
by S phase. On ageing at 190°C, S phase formation is completed within 12
h. The precipitates identified by 3DAP and TEM can be classified into (a) Li
rich clusters containing Cu and Mg, (b) a plate shaped metastable
precipitate (similar to GPB2 zones/S"), (c) S phase and (d) δ'
spherical particles rich in Li. The Zr containing alloy also contains
β' (Al3Zr) precipitates and composite β'/δ'
particles. The β precipitates reduce recrystallisation and grain growth
leading to fine grains and subgrains.
14.
Gao, N., M. J. Starink, et al. (2005). Microstructural Evolution in Pure
Aluminium and a 7034 Alloy Processed by Equal-Channel Angular Pressing. 9th
International Conference on Aluminium Alloys, Brisbane, Australia, Institute
of Metals and Materials Australasia Ltd.
Experiments were conducted to evaluate the microstructural evolution
occurring in pure aluminium and a spray-cast Al-7034 alloy after processing
through equal-channel angular pressing (ECAP). Electron back-scatter
diffraction (EBSD) was used to determine the grain boundary misorientations
and the texture after ECAP and differential scanning calorimetry (DSC) was
employed to evaluate the nature of thermal effects taking place during
heating. The results demonstrate there is an increase in the fraction of
boundaries having high angles of misorientation with increasing strain. For
pure aluminium, there is an S texture {122} <634> after 4 passes and a
brass texture {011} <211> after 8 passes. For the Al-7034 alloy, the
textures changes from a fibre <111>x texture in the as-received
condition to a <101>y after 1 pass, <111>y after 4 passes and
<100>z after 8 passes. For the Al-7034 alloy, the DSC analysis
identifies the occurrence of several thermal effects during heating
involving the formation, coarsening, dissolution and melting of the
n-phase.
15.
Gao, N., S. C. Wang, et al. (2005). "A comparison of grain size
determination by light microscopy and EBSD analysis." Journal of
Materials Science 40(18): 4971-4974.
In this paper, the application of electron backscattered diffraction (EBSD)
to the measurement of grain size for a low carbon steel and a diluted
Al-Cu-Mg alloy is reported. Results show that the accuracy of optical
microscopy analysis of grain size depends on sample preparation techniques,
etching procedures, and materials, where the visibility of a grain boundary
is a function of the technique used, and the microstructure components on or
close to the boundary. On the other hand, EBSD analysis has an advantage
over the optical examination in better imaging smaller grains and its result
is not dependent on etching and imaging techniques.
16.
Gao, N., T. G. Langdon, et al. (2006). Microstructure and texture
development in aluminium 7034 and 2024 alloys processed by ECAP. 2006 TMS
Annual Meeting, San Antonio, Texas, USA.
The evolution of microstructure and texture during equal channel angular
pressing (ECAP) of a spray-cast Al-7034 alloy and a conventionally cast
Al-2024 alloy were studied through the use of electron back-scatter
diffraction (EBSD) and differential scanning calorimetry (DSC).
Microstructural examination showed the grain sizes of both alloys were
reduced to -0.3-0.5 um through processing by ECAP. The experiments show
there is a relatively rapid increase in the fraction of low-angle grain
boundaries during the initial ECAP passes and a subsequent more gradual
increase in the fraction of high-angle grain boundaries in subsequent
passes. The crystallographic textures and their rotations during ECAP were
analysed. An analysis by DSC was used to identify the occurrence of thermal
effects involving the formation, coarsening and dissolution of the
precipitate phases and the occurrence of recrystallization. The heating and
ageing response of the materials both before and after ECAP were studied
using microhardness testing of the samples after interrupted heating and
ageing treatments.
17.
Gao, Y., M. Kumar, et al. (2005). "High-Cycle Fatigue of Nickel-Based
Superalloy ME3 at Ambient and Elevated Temperatures: Role of Grain-Boundary
Engineering." Metallurgical and Materials Transactions A
36A(12): 3325-3333.
High-cycle fatigue (HCF), involving the premature initiation and/or rapid
propagation of cracks to failure due to high-frequency cyclic loading,
remains a principal cause of failures in gas-turbine propulsion systems. In
this work, we explore the feasibility of using “grain-boundary
engineering” as a means to enhance the microstructural resistance to
HCF. Specifically, sequential thermomechanical processing, involving
alternate cycles of strain and annealing, was used to increase the fraction
of “special” grain boundaries and to break up the interconnected
network of “random” boundaries, in a commercial polycrystalline
Ni-based superalloy (ME3). The effect of such grain-boundary engineering on
the fatigue-crack-propagation behavior of large (~8 to 20 mm),
through-thickness cracks at 25 °C, 700 °C, and 800 °C was
examined. Although there was little influence of an increased special
boundary fraction at ambient temperatures, the resistance to near-threshold
crack growth was definitively improved at elevated temperatures, with
fatigue threshold stress intensities some 10 to 20 pct higher than at 25
°C, concomitant with a lower proportion (~20 pct) of intergranular
cracking.
18.
Garcia-Gonzalez, J. E. (2005). Fundamental study of the austenite formation
and decomposition in low-silicon, aluminum added TRIP steels, University of
Pittsburgh. PhD: 208.
TRIP (Transformation Induced Plasticity) steels are under development for
automotive applications that require high strength and excellent
formability. Conventional TRIP steels consist of a multiphase microstructure
comprised of a ferrite matrix with a dispersion of bainite and metastable
retained austenite. The high ductility exhibited by these steels results
from the transformation of the metastable retained austenite to martensite
during straining. In conventional TRIP steel processing, the multiphase
microstructure is obtained by controlled cooling from the α + γ
region to an isothermal holding temperature. During this holding, bainite
forms and carbon is rejected out into the austenite, which lowers the Ms
temperature and stabilizes the austenite to room temperature.In this
research project, a fundamental study of a low-Si, Mo-Nb added cold rolled
TRIP steel with and without Al additions was conducted. In this study, the
recrystallization of cold-rolled ferrite, the formation of austenite during
intercritical annealing and the characteristics of the decomposition of the
intercritically annealed austenite by controlled cooling rates were
systematically assessed. Of special interest were: (i) the effect of the
initial hot band microstructure, (ii) the formation of epitaxial ferrite
during cooling from the intercritical annealing temperature to the
isothermal holding temperature, (iii) the influence of the intercritically
annealed austenite on the formation of bainite during the isothermal holding
temperature, and (iv) the influence of the processing variables on the type,
amount, composition and stability of the retained austenite. During this
research study, techniques such as OM, SEM, EBSD, TEM, XRD and Magnetometry
were used to fully characterize the microstructures. Furthermore, a Gleeble
3500 unit at US Steel Laboratories was used for dilatometry studies and to
simulate different CGL processing routes, from which specimens were obtained
to evaluate the mechanical properties.
19.
Gardiola, B., C. Esling, et al. (2003). "EBSD Study of the γ to
α Phase Transformation in an CSP-HSLA Steel." Advanced
Engineering Materials 5(8): 583-587.
The compact strip production (CSP) is an industrial process for the
elaboration of high strength low alloy (HSLA) steels. This process has been
described in detail in previous contributions. The steel sheets are cast in
thin slabs and directly rolled to their final thickness in the austenitic
phase (γ -phase). Their metallurgical states at room temperature (in
the α - phase) are inherited by phase transformation from the high
temperature states. The ferritic states inherited influence the mechanical
behaviour of steels. In particular, ferritic textures determine the sheet
in-plane anisotropy. Therefore, the study of the mechanisms of phase
transformation is of a great industrial interest. In this contribution, we
present two different methods to determine the orientation relations based
on the measurement of individual orientations by electron backscattering
diffraction (EBSD). When a fraction of the high temperature phase was
retained at room temperature, the study was carried out by determining the
misorientation between neighbouring gamma and alpha grains. When there was
no (or few) gamma phase retained, the method consisted in comparing the
misorientation between neighbouring ferritic grains with the theoretical
misorientations between variants provided by NW and KS orientation
relations.
20.
Garmestani, H. and K. Harris (1999). "Orientation determination by EBSP
in an environmental scanning electron microscope." Scripta Materialia
41(1): 47-53.
Remarkable progress has been made in the single orientation measurement of
polycrystalline materials using scanning electron microscopy (SEM) (1,2,3).
The automation of this technique in the form of Orientation Imaging
Microscopy (OIM) provides materials scientists with a reliable technique of
texture and micro-texture characterization of materials at high vacuum
conditions (4,5). The technique is based on the acquisition of Electron
Backscattered Diffraction Patterns (EBSP) in the chamber of an SEM. These
diffraction patterns are formed in the same manner as Kikuchi patterns in
the TEM, but result from backscattering of electrons out of the top surface
of the sample. Hence they can be obtained from bulk samples. In this paper
we will discuss some of the unique capabilities provided by EBSP analysis at
elevated pressures and temperatures in an Environmental Scanning Electron
Microscope (ESEM). It was possible to obtain patterns with good quality for
water vapor pressures as high as 6 Torr for single crystals, and 3 Torr for
polycrystalline materials (NiAl grains with diameter up to 64 microns were
examined). With increasing pressure, polycrystalline diffraction patterns
degrade at a much higher rate than single crystal patterns.
21.
Garmestani, H., P. Kalu, et al. (1995). Microstructural Evolution and
Characterisation of Al-8090 Superplastic Materials. Microscopy and
Microanalysis, Jones and Begall Publishing.
22.
Garmestani, H., P. Kalu, et al. (1998). "Characterization of Al-8090
superplastic materials using orientation imaging microscopy." Materials
Science and Engineering A242: 284-291.
A fundamental understanding of the deformation mechanisms of superplasticity
requires a detailed characterization of the microstructure. For certain
studies, optical microscopy, transmission electron microscopy (TEM) and
scanning electron microscopy (SEM) techniques used in conventional mode may
be inadequate for detailed analysis. This paper presents the use of a newly
developed technique, ‘orientation imaging microscopy’ (OIM) in
characterizing the microstructure of an Al-8090 alloy deformed in uniaxial
tension to strains of 15, 70 and 660% at 520°C and 5x10-4
s-1 strain rate. In OIM the microstructure is constructed from
the measured crystal orientations obtained from points on the specimen
surface distributed in a hexagonal grid. Neighboring measurements with a
misorientation greater than a specified value, ϖ, misorientation angle
criteria (designated by the researcher) are deemed to define the location of
grain boundaries. These boundary lines can be interpreted as high angle
grain boundaries or subgrain boundaries depending on the value of ϖ. The
implications of the analyses on superplastic deformation are
discussed.
23.
Garzon, C. M. and A. P. Tschiptschin (2004). "New high temperature gas
nitriding cycle that enhances the wear resistance of duplex stainless
steels." Journal of Materials Science 39(23): 7101-7105.
A novel nitriding cycle inhibits nitride precipitation and leads to sharp
textures. It consists on cycling the specimen between two different
N2 partial pressures, PN2: a high pressure stage
(sorption stage) and a vacuum one (desorption stage). After nitriding,
microstructure, microtexture, hardness, nitrogen content, cavitation-erosion
(CE), wear resistance and pitting corrosion resistance of the duplex steel
were determined. Electron backscattering diffraction (EBSD), scanning
electron microscopy (SEM), wavelength dispersive spectroscopy (WDS) were
used to determine the properties of the austenitic steel. The cyclical
nitriding treatment leads to greater nitrogen contents in the surface, as
well as in the near surface region. Vickers hardness was greater in the
cyclical treated specimens. The new cyclical nitriding treatment leads to
austenitic cases with both higher microhardness and macrohardness which
guarantees a better surface load-bearing capacity, wear resistance
property.
24.
Gavard, L., F. Montheillet, et al. (1999). Microtextures in copper
undergoing dynamic recrystallization (DRX) in torsion. Twelfth International
Conference on Textures of Materials (ICOTOM 12), McGill University,
Montreal, Canada, NRC Research Press.
25.
Gavard, L., F. Montheillet, et al. (2000). "The Effect of Purity on
Dynamic Recrystallization in Austenitic Stainless-Steels." Materials
Transactions 41(1): 113-115.
26.
Gavriljuk, V. G., H. Berns, et al. (1999). "Grain Boundary
Strengthening in Austenitic Nitrogen Steels." Materials Science and
Engineering A 271(1-2): 14-21.
27.
Gee, J. S., W. P. Meurer, et al. (2004). "Quantifying Three-Dimensional
Silicate Fabrics in Cumulates Using Cumulative Distribution Functions."
Journal of Petrology 45(10): 1983-2009.
We present a new method for quantifying three-dimensional silicate fabrics
and the associated uncertainties from grain orientation data on three
orthogonal sections. Our technique is applied to the orientation of
crystallographic features and, hence, yields a fabric related to the
lattice-preferred orientation, although the method could be applied to
shape-preferred orientations or strain analysis based on passive linear
markers. The orientation data for each section are represented by their
cumulative distribution function, and an iterative procedure is used to find
the symmetric second-rank strain tensor that will simultaneously satisfy the
cumulative distribution functions observed on each section. For samples with
well-developed fabrics, this technique provides a much closer match to the
sectional data than do previous techniques based on eigenparameter analysis
of two-dimensional orientation data. Robust uncertainty estimates are
derived from a non-parametric bootstrap resampling scheme. The method is
applied to two cumulates: one with a well-developed fabric and the other
with a weak fabric, from the Stillwater complex, Montana. The silicate
petrofabric orientations obtained for these samples compare favorably with
independent direct estimates of the volume fabric from electron backscatter
diffraction and magnetic techniques.
28.
Geertruyden, W. H. V., H. M. Browne, et al. (2005). "Evolution of
Surface Recrystallization during Indirect Extrusion of 6xxx Aluminum
Alloys." Metallurgical and Materials Transactions A 36A (4):
1049-1056.
The fundamentals of coarse grain surface recrystallized structure formation
in extrusion of 6xxx aluminum alloys are not yet completely understood. The
objective of this article is to understand the metallurgical origins and
mechanisms of the formation of the peripheral coarse grain (PCG) structure
as the first step to understanding surface behavior of extruded aluminum
alloys. Small-scale indirect extrusion tests were performed in which
deformation parameters of strain, strain rate, and temperature were closely
controlled. The deformed material was characterized via traditional
metallography and orientation imaging microscopy (OIM) in order to
understand the influence of processing conditions and alloy chemistry on
surface grain formation. It was found that decreasing
recrystallization-inhibiting elements such as Cr as well as increasing the
starting extrusion temperature, extrusion ratio, and ram speed all increased
the depth of the PCG. Additionally, a mechanism for favorable coarse grain
formation at the surface of the extrudate is proposed based on
microstructure development during extrusion
29.
Geertruyden, W. H. V., S. R. Claves, et al. (2002). "Electron
Backscatter Diffraction Analysis of Microstructural Evolution in
Hot-Deformed 6xxx Series Aluminum Alloys." Metallurgical and Materials
Transactions A 33A(3): 693-700.
The electron backscatter diffraction (EBSD) technique is used to analyze the
crystallographic grain orientation of deformed microstructures for 6xxx
series aluminum alloy extrusions. In a partially extruded billet of
aluminum, deformation zones with different crystallographic characteristics
can be seen. Using compression testing performed on a Gleeble
thermal-mechanical simulator under various conditions, the formation of
different deformation zones is simulated. The EBSD technique is used to
characterize samples deformed in compression testing to analyze the
different deformation zones present in the extrusion process. Metal-flow
analysis using EBSD is also applied to study the influence of different die
designs on the surface structure of an extrudate. Microstructures from a
profile that was formed with different die designs are examined. Analysis of
a longitudinal weld present in typical hollow profiles is performed to
determine the effect of metal-flow conditions on the resultant texture in
the extrudate. The texture (or microtexture) measured from individual grains
can be correlated to the orientation changes that occur during
deformation.
30.
Geier, S., M. Schreck, et al. (1994). "Characterization of the
Near-Interface Region of Chemical-Vapor-Deposited Diamond Films on Silicon
by Backscatter Kikuchi Diffraction." Applied Physics Letters
65(14): 1781-1783.
31.
Geisler, H., I. Ziernet, et al. (2003). Potential and Limits of Texture
Measurement Techniques for Inlaid Copper Process Optimization. 2003
International Conference on Characterization and Metrology for ULSI
Technology, Austin, Texas, American Institute of Physics, Mellville,
NY.
For future technology nodes with shrunken interconnect dimensions, a
thorough texture analysis of the metal interconnects becomes increasingly
important in order to optimize and to control the inlaid-copper process. In
comparison to plane metal layers deposited on wafers, the microstructure of
the metal is more complicated in copper lines and vias which were produced
using an inlaid process. Therefore, advanced texture-measurement techniques
like X-ray microdiffraction, electron backscatter diffraction (EBSD), and
TEM combined with automated crystallography analysis (ACT) are needed to
obtain the required microstructure information. These complementary methods
are suitable to pick up local as well as integral information on the
crystallographic orientation of the copper interconnects and liner
materials. Potential and limits of the available techniques and the
respective instrumentation are discussed in this paper. Examples of
process-monitoring capabilities and of development support, especially with
regard to interconnect reliability, are presented.
32.
Geiss, R. H., A. Roshko, et al. (2003). Electron backscatter diffraction for
studies of localized deformation. Electron Microscopy: Its Role in Materials
Science. Mike Meshii Symposium. Proceedings of a Symposia, San Diego, CA,
USA, TMS - Miner. Metals & Mater. Soc.
Electron backscatter diffraction (EBSD) was used to study localized
deformation in two types of constrained-volume materials. We present a study
of deformation in narrow aluminum interconnects after low frequency, AC
cycling at high current density. Joule heating and differential thermal
expansion caused cyclic thermal straining, resulting in thermomechanical
fatigue. By quasi in-situ testing, we determined the evolution of the
crystallography of all grains and boundaries in the interconnect lines. The
results allowed us to formulate a mechanistic understanding of the
deformation process, including slip line formation and grain growth. In a
second study, we analyzed diffraction patterns from selectively oxidized,
multilayered AlGaAs/GaAs structures. Elastic strains associated with the
oxidation front in multilayered AlGaAs were characterized by EBSD Pattern
sharpness maps revealed the resulting strain field about the oxide growth
front, which we compared with finite element simulations. Quantitative
strain measurements were made comparing measurements of band widths on
processed images.
33.
Geiss, R. H., R. R. Keller, et al. (2005). TEM-Based Analysis of Defects
Induced by AC Thermomechanical versus Microtensile Deformation in Aluminum
Thin Films. Thin Films-Stresses and Mechanical Properties XI. Symposium, San
Francisco, California, USA, Materials Research Society.
Thin films of sputtered aluminum were deformed by two different experimental
techniques. One experiment comprised passing high electrical AC current
density through patterned Al interconnect lines deposited on
SiO2Si substrates. The other consisted of uniaxial mechanical
tensile deformation of a 1 mm thick by 5 µm wide free standing Al
line. In the electrical tests approximately 2 x 107 W/cm2 was
dissipated at 200 Hz resulting in cyclic Joule heating, which developed a
total thermomechanical strain of about 0.3 % per cycle. The tension test
showed a gauge length fracture strain of only 0.5 % but did display ductile
chisel point fracture. In both experiments, certain grains exhibited large,
> 30°, rotation away from an initial < 111 > normal orientation
toward < 001 >, based on electron backscatter diffraction (EBSD)
measurements in the scanning electron microscope (SEM). Transmission
electron microscopy (TEM) analysis of specimens from both experiments showed
an unusually high density of prismatic dislocation loops. In the
mechanically-tested samples, a high density of loops was seen in the chisel
point fracture zone. In cross sections of highly deformed regions of the
electrical test specimens, very high densities, > 1015/em3, of
small, < 10 nm diameter, prismatic loops were observed. In both cases the
presence of a high density of prismatic loops shows that a very high density
of vacancies was created in the deformation. On the other hand, in both
cases the density of dislocations in the deformed areas was relatively low.
These results suggest very high incidence of intersecting dislocations
creating jogs and subsequently vacancies before exiting the sample.
34.
Geist, V., G. Wagner, et al. (2005). "Investigations of the meteoritic
mineral (Fe,Ni)3P." Crystal Research and Technology
40(1/2): 52-64.
A survey is presented on some characteristic features of meteoritic
(Fe,Ni)3P which is an abundant and important minor phase of most
iron meteorites. This mineral (named schreibersite/rhabdite) plays a
decisive role during the formation of the so-called Widmanstätten
pattern. Different transmission as well as scanning electron microscopic
techniques have been applied to get more precise information about the real
structure of the phosphide crystals, their chemical composition and the
metal distribution across the phoshide/ kamacite interface. X- ray crystal
structure determinations have been performed for selected
(Fe,Ni)3P - cystals from various iron meteorites (Toluca, North
Chile, Watson, Orange River, Morasko, Agpalilik, Odessa, Canyon Diablo).
These experiments revealed a metal ordering, i.e. for the three
non-equivalent metal positions a different substitution of Fe by Ni has been
found. The perfection of the brittle (Fe,Ni)3P samples differs
appreciably and seems to be dependent on the thermal history of each
individual meteorite. Moreover, inside Ni-rich rhabdite crystals small
monocrystalline inclusions of CrN (carlsbergite) have been detected.
35.
Gelebart, L., J. Crepin, et al. (2004). "Identification of Crystalline
Behavior on Macroscopic Response and Local Strain Field Analysis:
Application to Alpha Zirconium Alloys." Journal of ASTM International
(JAI) 1(9): 17.
The purpose of this paper is to present an identification method of the
crystalline behavior of a material from a mechanical test performed on a
polycrystalline sample. Because of the lack of knowledge about its
crystalline behavior, this method is applied to a Zirconium alloy. This
identification is based on a finite element modeling of the microstructure,
and the results are compared to both the macroscopic and the microscopic
experimental results. On the microscopic scale, the plastic strains are
obtained using a micro-extensometry technique and the crystalline
orientation using an EBSD technique. In order to validate the method, an
identification is performed with only two free parameters: the evolutions of
the macroscopic and microscopic errors appear to be regular and exhibit a
well-defined minimum so that the parameters can be clearly
identified.
36.
Gemperle, A. and J. Gemperlova (1995). "Practical Accuracy of Grain
Misorientation Measurements by Kikuchi Line Technique." Ultramicroscopy
60(2): 207-218.
37.
Gemperlova, J., M. Polcarova, et al. (1995). "Determination of Grain
Misorientation from Laue Patterns." Journal of Physics D 28(1):
90-99.
38.
Genevois, C. (2004). Genesis of the microstructures during friction stir
welding of aluminium alloys of the series 2000 and 5000 and resulting
mechanical behavior, Institut National Polytechnique, 38 - Grenoble
(France): 170.
The 2024 alloy (Al-Cu-Mg) is used for minimizing the weight of
structural components in the transportation industry. However, this alloy is
not easy to weld by traditional techniques. Friction stir welding (FSW) is a
recently developed solid state process which removes the solidification
defects. In this study, the microstructures of FSW welds of this alloy were
finely characterized by SAXS, DSC, TEM, SEM, EBSD and optical microscopy. In
order to highlight the interactions between deformation, precipitation and
recrystallization, which all take place during the welding of the 2024
alloy, model experiments were carried out as well as a comparative study
between the alloys 5251 and 2024. The combination of the welding
characterisation and the model experiments allow to define the metallurgical
phenomena controlling the mechanical strength of the welded joints and their
microstructure. In addition, a detailed characterisation of the mechanical
behaviour of the welded joints was carried out, validated by a finite
element model.
39.
Genoud, J.-Y., E. Giannini, et al. (2001). "Material Developments in
Ag/Bi,Pb(2223), Ag/RE(123) and Ag/Tl(1223) tapes: texture in HTS."
Physica C 354: 327-332.
40.
Gerber, P., J. Tarasiuk, et al. (2002). Influence of the Rolling Reduction
on Static Recrystallization in Copper. ICOTOM 13, Seoul, Korea, Trans Tech
Publications Inc.
In order to explain texture evolution during annealing in pure copper,
texture and microstructure characteristics have been analyzed after
deformation at various rolling strains (between 70 and 98%) and after
partial annealing treatments. Texture evolution was followed by X-ray
diffraction, whereas local microstructural features, such as grain sizes,
inter and intragranular misorientations were followed by EBSD. It is shown
that there is a critical strain for which the recrystallization texture
changes from a mixed "deformation-recrystallization" type to a
strong Cube texture. These modifications are discussed in terms of possible
nucleation and growth mechanisms.
41.
Gerber, P., J. Tarasiuk, et al. (2003). "A quantitative analysis of the
evolution of texture and stored energy during annealing of cold rolled
copper." Acta Materialia 51(20): 6359-6371.
The experimental evolution of the global texture during
recrystallization of cold rolled copper is presented after various rolling
reductions. After presentation of the method used for the decomposition of
the orientation distribution functions obtained from X-ray diffraction
measurements into gaussian peaks, the behavior of each texture component is
studied. This quantitative analysis coupled with stored energy measurements
also obtained by X-ray diffraction allows the oriented nucleation and growth
mechanisms to be linked to stored energy variations. The proposed mechanisms
are then confirmed by local observations obtained by EBSD.
42.
Gerber, P., J. Tarasiuk, et al. (2004). Monte Carlo Modelling of
Recrystallization Mechanisms in Wire-Drawn Copper from EBSD Data. Second
Joint International Conference on Recrystallization and Grain Growth, ReX
& GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
In order to simulate the recrystallization process, Monte Carlo modelling
has been applied to the case of wire-drawn copper deformed to a moderate
strain. The complete experimental set of data was taken mainly from Electron
Back Scattered Diffraction measurements in a Scanning Electron Microscope.
Several nucleation hypothesis have been introduced and tested into the
model. It has been shown that nucleation, taking into account the sites
associated with the highest stored energy and highest local misorientation,
leads to the best results in terms of recrystallization microstructure and
texture. An important number of new orientations - that come only from
annealing twinning - are not reproduced with the model, indicating the major
role of this particular mechanism during the recrystallization
process.
43.
Gerber, P., S. Jakani, et al. (2004). Recrystallization Mechanisms in
Wire-Drawn Copper. Second Joint International Conference on
Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France,
Trans Tech Publications Ltd.
Wire-drawn Electrolytic Tough Pitch copper deformed at moderate strain has
been investigated with Electron Back Scattered Diffraction in a Scanning
Electron Microscope in order to evaluate the recrystallization mechanisms at
the meso-scale. Experimentally, it has been shown that the static
recrystallization takes place first in the highly deformed and misoriented
areas, in the intermediate regions of the wire. The grains related to the
<100> fiber nucleate and grow first in these regions, but some other
orientations (including the <111> oriented grains) - that have a
combined nucleation/growth potential - develop in second time. The annealing
twinning is active from the beginning of the recrystallization and tends to
randomize the final recrystallization texture.
44.
Gerber, P., T. Baudin, et al. (2004). Estimation of Stored Energy
Distribution from EBSD Measurements. Second Joint International Conference
on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France,
Trans Tech Publications Ltd.
Wire-drawn copper has been investigated with Electron Backscatter
Diffraction technique in a scanning electron microscope after deformation by
wire-drawing. In this paper, we show how to get qualitative information
about the deformation inhomogeneities related to the stored energy
distribution, from the analysis of the quality index. Furthermore, the
microstructural analysis in the wire diameter is completed using the quality
index distribution approach. A relation between the diameter of the wire and
stored energy distribution is then qualitatively set. In order to validate
the proposed method, the EBSD data are compared with the stored energy
values obtained from neutron diffraction measurements.
45.
Gerber, P., T. Baudin, et al. (2005). EBSD Study of Annealing Twinning
during Recrystallization of Cold Rolled Copper. Textures of Materials -
ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
In this work, EBSD (Electron Back Scattered Diffraction) measurements have
been performed on deformed, partially and fully recrystallized cold rolled
copper to 70 and 90 % reduction. The twin fraction as well as its existing
relation with the parent crystallographic orientation has been followed in
relation with respect to the recrystallized fraction. It has been shown
thanks to this quantitative analysis that annealing twinning is more active
when recrystallization nuclei slowly develop. The experimental observations
are briefly discussed according with the twins selection principles
[1].
46.
Germain, L., N. Gey, et al. (2005). "Analysis of sharp microtexture
heterogeneities in a bimodal IMI 834 billet." Acta Materialia
53(13): 3535-3543.
Regions with sharp hexagonal close-packed (hcp) local textures, named
macrozones, have been observed in an IMI 834 billet and analyzed in relation
to the bimodal alloy microstructure. They are clearly related to regions
with primary αp grains oriented around a main texture
component. The resulting αp microtexture is discussed
considering heterogeneous deformation and globularization of initial packets
of αp lamellae. Within an hcp macrozone, several prior
βgrain orientations were present at high temperature. The β phase
developed no sharp texture heterogeneities during α/ β working.
Clusters of β grains sharing close orientations and containing small
grains with high angle boundaries were observed. This β microtexture
can result from severe α/ β deformation of initially large prior
grains, associated with continuous dynamic recrystallization. By cooling,
the αs colonies inherited from the β grains and
surrounding the αp grains display several texture
components with the main one matching that of the αp phase.
This connection seems to be due to a variant selection influenced by the
presence of αpgrains.
47.
Germain, L., N. Gey, et al. (2005). β→αs variant selection
in sharp hcp textured regions of a bimodal IMI834 billet. Textures of
Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
Regions with sharp local textures, called macrozones, have been
characterised in a bimodal IMI834 billet, containing 30% of primary αp
grains surrounded by secondary αs colonies. It is shown that
the αs colonies have been inherited according to a strong variant
selection during the β→αs phase transformation.
In each observed macrozone, the favoured variants have in average their
c-axes in the same macroscopic direction as the αp grains. A
detailed analysis of neighbouring αp grains and
αs variants clearly shows that the variants favoured at
β/αp boundaries are those able to share their c-axes
with a neighbouring αp grain. The sharpness of such a variant selection
mechanism is strongly related to the local orientation distribution of
neighbouring αp/β grains at high temperature. This
explains the differences in variant selection sharpness observed from one
macrozone to the other.
48.
Germain, L., N. Gey, et al. (2005). "An automated method to analyze
separately the microtextures of primary αp grains and the
secondary αs inherited colonies in bimodal titanium
alloys." Materials Characterization 54(3): 216-222.
A method was developed to automatically recognize the orientations of
primary αp grains and secondary αs
colonies of a bimodal titanium alloy, on the orientation map. Both
populations of grains are dissociated by correlating the Electron Back
Scattering Diffraction data with the corresponding Back Scattered Electron
image on which a high chemical contrast is observed between the
αp and (αs+ βresidual)
phases. The whole data processing is successfully applied to a large EBSD
map of a bimodal IMI 834 billet. This allows to discuss the contribution of
αp grains and αs colonies to the sharp
texture heterogeneities observed in the billet.
49.
Gertsman, V. Y. and J. A. Szpunar (1998). "On the Grain-Boundary
Character Distributions and Grain-Boundary Network Topology (Grain-Boundary
Statistics in Materials Susceptible to Annealing Twinning, Revisited)."
Scripta Materialia 38(9): 1399-1404.
50.
Gertsman, V. Y. and J. C.H. Henager (2003). "Grain Boundary Junctions
in Microstructure Generated by Multiple Twinning." Interface Science
11: 403-415.
The microstructure of a Cu-Ni alloy after static recrystallization was
investigated using electron backscatter diffraction in a scanning electron
microscope and the existence of orientationally related clusters of
crystallites formed by multiple twinning has been established. Grain
boundary and triple junction character within the clusters are analyzed.
While the outer boundaries of the cluster are crystallographically random,
all the inner boundaries have Σ3n misorientations. A newly
developed crystallographic theory of triple junctions and multicrystallite
ensembles consisting of CSL boundaries is used to describe the structure of
the cluster. The presence of an a is not equal to1 triple junction is
confirmed. Apparently, the microstructure of recrystallized materials
susceptible to annealing twinning consists of multiple-twinned clusters. The
cluster size cannot be reduced to the “grain size excluding
twins.”
51.
Gertsman, V. Y. and S. M. Bruemmer (2001). "Study of Grain Boundary
Character Along Intergranular Stress Corrosion Crack Paths in Austenitic
Alloys." Acta Materialia 49: 1589-1598.
Samples of austenitic stainless alloys were examined by means of scanning
and transmission electron microscopy. Misorientations were measured by
electron backscattered diffraction. Grain boundary distributions were
analyzed with special emphasis on the grain boundary character along
intergranular stress corrosion cracks and at crack arrest points. It was
established that only coherent twin Σ3 boundaries could be considered
as “special” ones with regard to crack resistance. However, it
is possible that twin interactions with random grain boundaries may inhibit
crack propagation. The results suggest that other factors besides
geometrical ones play an important role in the intergranular stress
corrosion cracking of commercial alloys.
52.
Gertsman, V. Y., K. Tangri, et al. (1994). "On the Grain-Boundary
Statistics in Metals and Alloys Susceptible to Annealing Twinning."
Acta Metallurgica et Materialia 42(6): 1785-1804.
53.
Gertsman, V. Y., R. Z. Valiev, et al. (1985). "On the Energy Change
During the Grain-Boundary Structure Recovery from Non-Equilibrium State to
Equilibrium State." Physica Status Solidi A 91(2):
K119-K124.
54.
Gey, N. and M. Humbert (2002). "Characterization of the variant
selection occurring during the α→β→α phase
transformations of a cold rolled titanium sheet." Acta Materialia
50: 277-287.
The fact that a cold rolling prior to an α→ β→α
transformation sequence causes the sharpening of the inherited
αtextures is analyzed. A restitution method is used to evaluate the
intermediate β textures which allowed us to discuss the occurrence of
variant selection in the β→α transformation. It appears
that cold rolling prior to the α → β transformation makes
the high temperature β texture sharper, with a density reinforcement
around the {112}/{11-2}<111> components and further the variant
selection occurring in the β→α phase transformation becomes
stronger. The local texture analysis obtained by EBSD leads to the same
results and is used to characterize the variant selection occurring in the
β→α transformation.
55.
Gey, N. and M. Humbert (2003). "Specific analysis of EBSD data to study
the texture inheritance due to the β → α phase
transformation." Journal of Materials Science 38(6):
1289-1294.
A specific processing of EBSD data is proposed to study the β →
α texture inheritance of α titanium or α zirconium alloys. A
non standard misorientation map is calculated to localise the colonies
inherited from the same parent β grain. The calculation of the parent
orientation from its inherited variants detailed in previous works has been
adapted to the data obtained from an automated EBSD analysis. Finally, a
method to derive the orientation map of the parent β phase from that of
the α inherited phase is proposed. The resulting α and β COMs
are used to study some aspects of the variant selection occurring in the
β → α transformation of a T40 sample.
56.
Gey, N., B. Petit, et al. (2005). "Electron Backscattered Diffraction
Study of ε/αMartensitic Variants Induced by Plastic
Deformation in 304 Stainless Steel." Metallurgical and Materials
Transactions A 36A(12): 3291-3299A.
The electron backscattered diffraction (EBSD) technique has been used to
assess crystallographic features of the residual γ phase and the
strain-induced ε/α' martensites in a 304 stainless steel,
tensile tested to 10 pct strain at T = -60°C. The martensitic
transformation rate varies according to the γ-grain orientation
against the applied stress and the g-grain size. The α'
-transformation textures as well as the γ-misorientation spreads
observed in specific γ-grain orientations have been analyzed. Large
misorientation spreads are observed in the less-transformed γ grains.
This reveals an important crystallographic slip activity, even if less
strain-induced martensite has been formed. A strong γ - > α
variant selection was detected in the cube- and Goss-oriented γgrains
for which the transformation is less developed. For the {110} < 111 >
and copper-oriented γ grains, the amount of a martensite is
significantly higher and the γ - > α variant selection is
less pronounced. This variant selection is then analyzed on at a local scale
and is related to the presence of {111}γ localized
deformation bands on which further ε/α' martensites have
nucleated.
57.
Gey, N., M. Humbert, et al. (2002). Analysis of the ß to
αVariant Selection in a Zy-4 Rod by Means of Specific Crystal
Orientation Maps. ICOTOM 13, Seoul, Korea, Trans Tech Publications
Inc.
A specific analysis of the α inherited Crystal Orientation Map (COM)
is proposed to study the ß to α texture inheritance of a Zy-4
rod. In particular it is shown that the αcolonies inherited from each
parent grain can systmatically be identified on the α Map by
considering the misorientations between pixels. Once identified, the
orientations of these colonies are used to calculate the orientation of
their common ß grain. Finally, the orientation data of the parent
phase can also be displayed as α COM. The ß COM shows that at
high temperature, the ß grains were mainly oriented around the
<111> //AD fibre. Moreover, the analysis of the parent and the
inherited COM, makes clear that each ß grain has preferentially
transformed into different variants belonging each to the <11.0> //AD
fibre. This variant selection is responsible for the sharp α texture
of the Zy-4 rod after treatment in the ß field.
58.
Gholinia, A., F. J. Humphreys, et al. (2002). "Production of ultra-fine
grain microstructures in Al-Mg alloys by conventional rolling." Acta
Materialia 50(18): 4461-4476.
The conditions under which micron-scale grain structures can be developed in
two Al-3%Mg alloys by a process of continuous recrystallization, during
rolling and plane strain compression to large strains, have been
investigated using high resolution electron backscatter diffraction (EBSD).
In an Al-Mg-Cr-Fe alloy, it was found that a lower limit to the processing
temperature for forming ultra-fine grain structures is imposed by the low
mobility of grain boundaries, whilst an upper limit is imposed by grain
growth. In an Al-Mg-Sc-Zr alloy containing stable second-phase dispersoid
particles, a fine-grained microstructure is formed only at larger strains
and higher temperatures due to the interaction of grain boundaries with the
dispersoids. It is concluded that although micron-scale grain structures can
be produced in Al-3%Mg alloys by deformation processing in plane strain
compression, the processing window, which is controlled by both the solute
and particle content, is severely restricted.
59.
Gholinia, A., F. J. Humphreys, et al. (2002). The Texture of Ultra-Fine
Grained Al-Mg Alloys. ICOTOM 13, Seoul, Korea, Trans Tech Publications
Inc.
Two Al-3%Mg alloys, one containing a fine dispersion of stable Al-Sc-Zr
particles, have been deformed to large strains in plane strain compression
at a range of temperatures. The present paper disusses the development of
texture during the deformation processing of these alloys. Microstructures
and textures have been measured by high resolution electron backscatter
diffraction (EBSD) in a FEGSEM. At low deformation temperatures, typical
banded deformation microstructures and rolling textures are developed in
both alloys, and the rolling textures persist at high strains, even when
approximately equiaxed "ultra-fine" grain structures are formed by
continuous recrystallization. However, as the deformation temperature is
increased, a stronger cube texture develops in the alloy which does not
contain the fine particle dispersion. The increase in cube texture
correlates with an increase in grain size due to dynamic grain growth, and
there is evidence that cube-oriented grains become significantly larger than
others
60.
Gholinia, A., P. B. Prangnell, et al. (2000). "The Effect of Strain
Path on the Development of Deformation Structures in Severely Deformed
Aluminum Alloys Processed by ECAE." Acta Materialia 48:
1115-1130.
Equal channel angular extrusion (ECAE) has been used to investigate the
formation of sub-micron grain structures in Al- alloys deformed to
ultra-high plastic strains by different strain paths. The different strain
paths were obtained by rotating billets through 0, 90, and 1808 between each
extrusion cycle. High resolution EBSD analysis has been employed to measure
the boundary misorientations within the deformation structures. This has
highlighted great differences in the evolution of the deformed state, as a
function of the strain path, even after effective strains as high as 16. It
has been demonstrated that the most effective method of forming a submicron
grain structure by severe plastic deformation is to maintain a constant
strain path. Processing routes involving a 1808 rotation reverse the shear
strain every second pass and this prevents the build up of significant
numbers of new high angle boundaries. When a sample is processed with an
alternate clockwise and anticlockwise 908 rotation, between each extrusion
cycle the billet is deformed on two shear planes, each of which experiences
half the total strain, compared to the single shear plane when there is no
rotation. This reduces the rate of formation of high angle boundaries. With
a constant clockwise 908 rotation the sample is also deformed on two
alternate shear planes, but the total strain becomes redundant every fourth
extrusion cycle. However, in this case each shear is reversed out of
sequence after first deforming the billet on the alternate shear plane. This
appears to be a much more effective means of forming new high angle
boundaries than 1808 rotation, where the shear strain is immediately
reversed each alternate cycle, but is still less ecient than
deformation with a constant strain path.
61.
Gignac, L. M., C. E. Murray, et al. (2002). A COMPARISON OF GRAIN SIZE
MEASUREMENTS IN AL-CU THIN FILMS: IMAGING VERSES DIFFRACTION TECHNIQUES.
Microscopy and Microanalysis 2002, Québec City, Québec,
Canada, Cambridge University Press.
62.
Ginsztler, J., S. W. Nam, et al. (2004). "Factors affecting the change
of subgrain size of 15Mo3 steel during creep." Materials at High
Temperatures 21(4): 187-192.
15Mo3 type steel samples were subjected to creep loading at 550ring cree C
in order to investigate the development of microstructure and the effect of
the carbides on the creep process. Electron microscopic observations have
shown that relatively small subgrains are formed up to the secondary stage
of creep deformation. As the creep progresses, due to the growth of
carbides, the average distance between the carbides is increased. This
increased the mean free path of moving dislocations, in turn the size of the
subgrain is also increased. This microstructural change is also verified by
EBSD technique which shows the variation of the configuration of grain
boundaries.
63.
Giocondi, J. L., G. S. Rohrer, et al. (2003). Orientation Dependence of the
Photochemical Reactivity of BaTi 4O 9. Solid-State
Chemistry of Inorganic Materials IV, Boston, MA, United States.
BaTi4O9 is a photocatalyst with a pentagonal prism
tunnel structure. It has been hypothesized that the tunnels promote the
separation of photogenerated carriers and, therefore, lead to the spatial
separation of oxidation and reduction half reactions. This hypothesis has
been tested by observing the distribution of reduced and oxidized reaction
products on BaTi4O9 surfaces over a wide range of
orientations. The surface orientations were determined by electron
backscattered diffraction and atomic force microscopy was used to examine
the structure of the surface both before and after the deposition of
reaction products. Reduction products (Ag0) are distributed
uniformly. The distribution of oxidation products (PbO2) is also
not correlated to the surface orientation or to the orientation of the
tunnels with respect to the surface. Based on these observations, we
conclude that the runnels in this structure do not separate photogenerated
charge carriers and that this mechanism is not responsible for this
compound's relatively high photocatalytic activity.
64.
Gironès, A., P. Villechaise, et al. (2004). "EBSD studies on the
influence of texture on the surface damage mechanisms developed in
cyclically loaded aged duplex stainless steels." Materials Science and
Engineering A 387-389: 516-521.
Interrupted cyclic deformation tests up to 20% of fatigue life were
performed on electropolished specimens of a thermally aged superduplex
stainless steel. Crystallographic orientation results obtained by electron
back-scattering diffraction analysis allowed to determine the individual
orientation of each individual grain as well as the plastically active slip
systems. Electron back-scattering diffraction results demonstrate the
requirement for the accomplishment of several conditions for a slip system
to become active. These conditions were found to be different for austenite
and ferrite.
65.
Gladstone, T. A., J. C. Moore, et al. (1999). "Fabrication of biaxially
textured Ni substrates and LaNiO3 buffer layers for Tl-1223 thick
films." IEEE Transactions On Applied Superconductivity 9(2):
2252-2255.
66.
Gladstone, T. A., J. C. Moore, et al. (2001). "Grain boundary
misorientation and thermal grooving in cube-textured Ni and Ni-Cr
tape." IEEE Transactions On Applied Superconductivity 11(1):
2923-2926.
67.
Glass, S. J., J. R. Michael, et al. (1998). Characterization of
Microstructure and Crack Propagation in Alumina using Orientation Imaging
Microscopy (OIM). Ceramic Microstructure: Control at the Atomic Level. A. P.
Tomsia and A. Glaeser. New York, Plenum Press: 803-813.
Structure-property relationships form the basis for understanding and
predicting materials behavior. Conventional studies of polycrystalline
materials have usually focused either on descriptions of the morphological
aspects of the microstructure, such as grain size and shape, or on the
chemistry and structure of individual boundaries using transmission electron
microscopy (TEM). TEM, while capable of determining the misorientation of
adjacent grains, can practicably provide information only for a small number
of grain boundaries. Clearly a more complete description of the structure of
a polycrystal requires the lattice orientations of a statistically
significant number of grains, coupled with morphological aspects of the
microstructure, such as grain size and shape. This description can be
obtained using a relatively new technique known as orientation imaging
microscopy (OIM), which utilizes crystallographic orientation data obtained
from Backscattered Electron Kikuchi patterns (BEKP), which are collected
using a scanning electron microscope. This paper describes the general OIM
results for 99.7 and 99.99% A1203 samples with grain sizes ranging from 4 to
27 um. The results include image quality maps, grain boundary maps, pole
figures, and lattice misorientations depicted on MacKenzie plots and in
Rodrigues space. Results were good in that high quality BEKPs were obtained
from all specimens. The images and data readily reveal the grain morphology,
texture, and grain boundary structure. Subtle differences in texture and
grain boundary structure, as defined by crystallite lattice misorientations,
are observed for the different alumina specimens. Distributions of
misorientations for cracked boundaries in alumina are compared to the bulk
distribution of boundaries and generally larger misorientations are
observed.
68.
Glass, S. J., V. R. Vedula, et al. (1999). Application of electron
backscattered diffraction (EBSD) and atomic force microscopy (AFM) to
determine texture, mesotexture, and grain boundary energies in ceramics.
ICOTOM 12, Montreal, Quebec, Canada, National Research Council of Canada,
Building M-55, Ottawa, ON K1A 0R6, Canada.
Crystallographic orientations in alumina
(Al2O3) and magnesium aluminate spinel
(MgAl2O4) were obtained using electron backscattered
diffraction (EBSD) patterns. The texture and mesotexture (grain boundary
misorientations) were random and no special boundaries were observed. The
relative grain boundary energies were determined by thermal groove
geometries using atomic force microscopy (AFM) to identify relationships
between the grain boundary energies and misorientations.
69.
Glavicic, M. G., A. A. Salem, et al. (2004). "X-ray line-broadening
analysis of deformation mechanisms during rolling of commercial-purity
titanium." Acta Materialia 52: 647-655.
X-ray line-broadening techniques were used to establish deformation
mechanisms in textured commercial purity (CP) titanium specimens that were
rolled at various temperatures. The results indicated that conventional
line-broadening techniques developed specifically for polycrystalline
powders could be used on textured materials to deduce the slip-system
activity and dislocation density that develop during thermomechanical
processing if appropriate averaging procedures are followed. The deduced
slip-system activity and densities revealed a transition in deformation
behavior from a heavily-twinned to an untwinned mode with an increase in
deformation temperature for CP titanium.
70.
Glavicic, M. G., P. A. Kobryn, et al. (2003). "A (automated) method to
determine the orientation of the high-temperature beta phase from measured
EBSD data for the low-temperature aplha phase in Ti-6Al-4V." Materials
Science and Engineering A 346 (351)(1-2): 50-59 (258-264).
A method was developed to determine the orientation of the
high-temperature beta phase from measured electron-backscatter diffraction
(EBSD) data for the low-temperature alpha phase in Ti-6Al-4V. This technique
is an improvement over existing methods because it does not require a prior
knowledge of the variant selection process and can accommodate variants from
adjacent beta grains being incorporated in the data set submitted for
analysis. It is a general method and therefore can be used to examine
texture relationships in materials other than Ti-6Al-4V which undergo a
burgers-type phase transformation.
71.
Glavicic, M. G., P. A. Kobryn, et al. (2003). "Texture evolution in
vacuum arc remelted ingots of Ti-6Al-4V." Materials Science and
Engineering A 346(1-2): 8-18.
The textures of the alpha and beta phases of a production-scale
Ti-6Al-4V VAR ingot were determined using orientation imaging microscopy
(OIM). Alpha-phase textures were determined directly from specimens that
were cut from various regions of the ingot. To determine the texture of the
beta-phase, the measured orientation of the alpha-phase variants from a
number of prior-beta grains and specialized analysis software, which was
based on the burgers relation between the alpha and beta phases, were
utilized. The results of the analysis demonstrated that the columnar grains
in the ingot had formed as a result of solidification of the beta phase
along <100> peferred-growth directions. By contrast, the equiaxed
grains at the center of the ingot had random alpha and beta-phased
textures.
72.
Glavicic, M. G., P. A. Kobryn, et al. (2004). "Validation of an
automated EBSD method to deduce the ß-phase texture in
Ti–6Al–4V with a colony-α microstructure." Materials
Science and Engineering A 385(1-2): 372-376.
An automated method to determine the texture of the ß-phase in
Ti–6Al–4V using measured α-phase
electron-backscatter-diffraction data (EBSD) was validated by comparing the
deduced texture with the texture measured directly using X-ray diffraction.
The deduced a-phase-variant frequency distribution revealed that all
variants were not equally probable.
73.
Gleichmann, R., D. G. Ast, et al. (1985). "Recovery of Edge-Defined
Film-Fed Grown Silicon - Dislocation Twin Boundary Interaction and
Mechanisms for Twin-Induced Grain-Boundary Formation." Philosophical
Magazine A 51(3): 449-467.
74.
Gleiter, H. (1982). "On the Structure of Grain-Boundaries in
Metals." Materials Science and Engineering 52(2):
91-131.
75.
Glez, J. C. and J. H. Driver (2003). An EBSD study of sub-grain structure
development in hot formed Al-1%Mn crystals. Thermec' 2003, Leganés,
Madrid, Spain, Trans Tech Publications Ltd.
Hot PSC (channel-die) tests have been carried out to large strains
(1.5) on 3 orientations of Al-1%Mn crystals, Bs {110}<112>, S
{123}<412> and U {110}<110>, using a wide range of temperatures
and strain rates (or Zener-Holloman parameter Z). The deformation
substructures are characterized by EBSD orientation mapping in terms of
sub-grain sizes δsub-grain misorientations and their frequency
distributions over large areas. The sub-grain sizes respect the linear
relation between 1/δand InZ but with significant orientation
dependency. The largest orientations are found in the Bs orientation at all
Z and the smallest in the S orientation at high strain rates. Sub-grain
misorientations increase rapidly with strain 3 to 4° then approximately
stabilise after strains of 0.5 or1. Some high angle boundaries (>10°)
are formed with frequencies about 10-2 to
10-3.
76.
Glez, J. C. and J. H. Driver (2003). "Substructure development in hot
plane strain compressed Al-1%Mn crystals." Acta Materialia
51(10): 2989-3003.
Hot PSC (channel-die) tests have been carried out to large strains
(1.5) on 3 orientations of Al-1%Mn crystals, Bs {110} <112>, S
{123}<412> and U {110}<110>, using a wide range of temperatures
and strain rates (or Zener-Holloman parameter Z). The deformation
substructures are characterized by EBSD orientation mapping in terms of
sub-grain sizes δsub-grain misorientations and their frequency
distributions over large areas. The sub-grain sizes respect the linear
relation between 1/δand InZ but with significant orientation
dependency. The largest orientations are found in the Bs orientation at all
Z and the smallest in the S orientation at high strain rates. Sub-grain
misorientations increase rapidly with strain 3 to 4° then approximately
stabilise after strains of 0.5 or1. Some high angle boundaries (>10°)
are formed with frequencies about 10-2 to 10-3. Many
of the size effects can be attributed to an enhanced rate of sub-boundary
generation in the case of the unstable grain orientations.
77.
Glowacki, B. A., M. E. Vickers, et al. (2002). "Texture development in
long lengths of NiFe tapes for superconducting coated conductor."
Journal of Materials Science 37(1): 157-168.
A highly oriented cubic texture (full width at half maximum
<10°) has been formed in long length NiFe tapes. The X-ray
diffraction (XRD), electron back-scattered patterns (EBSP) and optical
microscopy (OM) techniques have been used in assessing the surface and
volume texture and also the surface morphology of these kilometer long NiFe
substrates. This texture was formed under a range of conditions including
dynamic annealing in a reduced atmosphere and static annealing in hydrogen
and in a vacuum. Heat treatment for excessive times in vacuum tends to
roughen the surface and should be avoided. Mechanical polishing can induce
an additional undesirable texture, but electropolishing gives smooth tapes
with good texture.
78.
Go, J., M. Militzer, et al. (2004). "Microstructure evolution during
the annealing of cold rolled AA6111." JOM 56(11): 165-166.
The heat-treatable Al-Mg-Si-Cu alloy AA6111 is one of the main
aluminum choices for automobile sheet skin due to its excellent combination
of paint bake hardening response and high formability. In the commercial
processing for this alloy, fine and closely spaced precipitates that
developed during hot rolling and subsequent coiling processes can retard the
evolution of recrystallized microstructure by suppressing the movement of
high angle boundaries. On the other hand, large primary Fe-containing
constituent particles can promote recrystallization via
particle-stimulated-nucleation (PSN). In an effort to clarify the
interactions between these microstructural processes, a series of isothermal
annealing experiments have been conducted on cold rolled AA6111 with
systematically varied precipitation states. The evolution of microstructure,
both in terms of the recrystallized grain size distribution and spatial
distribution of second phases are characterized using a variety of
experimental techniques including EBSD grain mapping, electron channelling
contrast in SEM, optical microscopy and resistivity measurements. The
results indicate that the recrystallization kinetics are severely retarded
irrespective of prior aging conditions.
79.
Godec, M., M. Jenko, et al. (2006). "Characterisation of
crystallisation in amorphous soft magnetic Fe74
Si11B14Ni1 powders by EBSD method."
Materials Science and Engineering B 129(1-3): 31-38.
Amorphous Fe74Si11B14Ni1
soft magnetic powder was produced by water atomisation. Crystallisation of
amorphous powder was studied using multi-technique approach based on
electron beams, including high resolution transmission electron microscopy
(HRTEM) and electron backscatter diffraction (EBSD). It has been found that
annealing of the amorphous Fe-Si-B powder at a temperature of 500°C
leads to the formation of α-Fe phase in the form of two, three and
four-branch dendritic grains. The Fe2B boride is crystallised at
temperatures of over 500°C. In spite of the drift problem associated
with EBSD, which is not yet resolved in any commercial EBSD system, the
technique is very powerful and shows great promise as a high resolution
characterisation method
80.
Godet, S., B.-K. Kim, et al. (2003). Microtextural study of variant
selection by EBSD in a bainitic steel containing retained austenite.
International Conference on Martensitic Transformations, Espoo, Finland, EDP
Sciences.
The phenomenon of variant selection in a bainitic steel containing
retained austenite was investigated. The steel was hot-rolled below the Tnr
to true strains of epsilon = 0.2 and epsilon = 0.8 in the austenitic
temperature range. The orientation relationships between bainite and
austenite are expressed in Rodrigues space. A strain of 0.2 is shown to be
insufficient to induce variant selection. A hot deformation of 0.8 leads to
a much smaller number of variants being created, which are shown to be
related to the slip systems active during austenite deformation.
81.
Godet, S., J. C. Glez, et al. (2004). "Grain-scale characterization of
transformation textures." Journal of Applied Crystallography
37(pt. 3): 417-425.
Orientation relationships during the austenite-to-ferrite (gamma
-to- alpha) phase transformation were investigated using electron
back-scattered diffraction (EBSD) on a bainitic steel containing retained
austenite. The steel was hot rolled within the austenite phase field, but
below the 'no-recrystallization' temperature, to two different strains. The
observed orientation relationships between the bainite and retained
austenite are expressed in Rodrigues-Frank space. The exact Kurdjumov-Sachs
relation was never found. The local spread of orientation in the parent
austenite (owing to deformation) is seen to be inherited by the bainite.
This is attributed to the displacive mode of transformation to bainite. The
influence of austenite prior deformation on the occurrence of variant
selection was also studied. It is shown that a critical strain is necessary
in order to observe a significant amount of variant selection.
82.
Godet, S., Y. He, et al. (2005). Orientation Relationships and Variant
Selection During the γ-to-αb Transformation in a
Hot-Rolled TRIP Steel. Solid to Solid Phase Transformations in Inorganic
Materials 2005, Phoenix, Arizona, USA, TMS.
The transformation behavior of a
0.22wt.%C-1.50wt.%Mn-1.56st.%Si-0.045wt.%Nb TRIP steel was studied after
controlled rolling. Deformation below the no-recrystalllization temperature
was employed to strain the prior austenite. Using automated EBSD techniques,
both the retained austenite and bainite orientations were measured; the
orientation relationships between these phases are represented in pole
figure form. The observed orientations are compared to the predictions
associated with various correspondence relationships reported in the
literature. The bainite does not follow any of these predictions exactly and
exhibits a continuous spread, mainly between two coplanar Kurdjumov-Sachs
variants. Moreover, the initial spread of orientation in the parent
austenite grains rendered the determination of a precise correspondence
relationship somewhat difficult. The occurrence of variant selection during
the nucleation and growth of bainite within deformed austenite grains is
illustrated, and the observations are compared to the predictions obtained
from a dislocation-based model.
83.
Godet, S., Y. He, et al. (2005). Multiscale Characterisation of the
Transformation Texture in a High Performance Steel. Textures of Materials -
ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
The orientation relationships operating during the austenite (FCC)
to BCC phase transformation were investigated in a high performance steel
using X-ray and electron diffraction techniques and employing several length
scales. These steels contain some retained austenite that permits the direct
comparison of the textures of the parent (austenite) and product (ferrite,
bainite, martensite) phases. X-ray diffraction allowed the global texture of
the rolled parent austenite phase to be determined as well as that of its
transformation product. EBSD techniques permitted study of the orientation
relationships on a local scale. The observed correspondence relations are
expressed in Rodrigues-Frank space. The exact Kurdjumov-Sachs relation was
never found. The local spread of orientation in the parent austenite (due to
deformation) is seen to be inherited by the bainite. This is attributed to
the displacive mode of transformation to bainite. The influence of prior
deformation of the austenite on the occurrence of variant selection was also
studied. It appears that a critical strain is necessary to produce a
significant amount of variant selection.
84.
Godfrey, A. (2004). "Edge preservation near triple junctions during
orientation averaging of EBSP data." Scripta Materialia 50(8):
1097-1101.
A feature-based methodology is given for evaluating the dependence
of the modified Kuwahara filter on the orientation noise level. Inspection
of simulated orientation maps of dislocation cell microstructures suggests a
further modification that gives improved angular resolution whilst
maintaining edge preservation near triple junctions.
85.
Godfrey, A. and N. C. K. Lassen (2000). "Unsupervised approval criteria
for automated EBSP investigation of deformed metals." Journal of
Microscopy 197(Pt. 3): 249-259.
Unsupervised approval criteria have been investigated for
orientations gathered from cold deformed samples (medium to high strain
range) using the electron backscattering pattern technique. For such
samples, the dislocation cell-size is on the order of the available
step-size and pattern quality is generally low. Approval criteria for
assessing the validity of measured orientations under these conditions were
determined using, as a calibration, channel die cold deformed single
crystals of stable orientations. In all cases, approval criteria based on an
indexing confidence measure are found to be preferable. Different criteria
are suggested, depending on whether the orientation data are subsequently to
be used for texture analysis, or for a misorientation angle-based analysis.
The latter is illustrated by an investigation of the number of deformation
generated high angle boundaries introduced during a 90% cold reduction of a
polycrystalline sample.
86.
Godfrey, A., G. L. Wu, et al. (2002). Characterisation of Orientation Noise
during EBSP Investigation of Deformed Samples. ICOTOM 13, Seoul, Korea,
Trans Tech Publications Inc.
For quantitative investigations of deformed materials using the
electron backscatter pattern (EBSP) technique, the angular resolution limit
of the technique, resulting in an 'orientation noise' superimposed on the
measurements, still presents many problems. In order to better understand
EBSP data, particularly on highly deformed samples, it is necessary to
quantify the extent of the orientation noise. However, unlike the case of
single crystals, it is not possible to directly measure the orientation
noise. Some techniques are suggested for estimating the orientation noise
level for deformed samples, and examples given of cases where a quantitative
knowledge of the orientation noise level can be used to assist in the design
and interpretation of EBSP experiments of deformed samples.
Characterisation of Orientation Noise
during EBSP Investigation of Deformed Samples. ICOTOM 13, Seoul, Korea,
Trans Tech Publications Inc.
For quantitative investigations of deformed materials using the
electron backscatter pattern (EBSP) technique, the angular resolution limit
of the technique, resulting in an 'orientation noise' superimposed on the
measurements, still presents many problems. In order to better understand
EBSP data, particularly on highly deformed samples, it is necessary to
quantify the extent of the orientation noise. However, unlike the case of
single crystals, it is not possible to directly measure the orientation
noise. Some techniques are suggested for estimating the orientation noise
level for deformed samples, and examples given of cases where a quantitative
knowledge of the orientation noise level can be used to assist in the design
and interpretation of EBSP experiments of deformed samples.
87.
Godfrey, A., W. Liu, et al. (2005). Investigation of Local Texture
Correlations in Bi-2223 High Temperature Superconductor Tapes. Textures of
Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
In this paper we report a study using fully automated EBSP
orientation measurements on the texture and microstructure of fully
processed Bi-2223 tapes produced by the powder-in- tube method. For the
automated analysis a new unit cell describing the quasi-tetragonal Bi-2223
phase has been developed. The texture data confirm that a strong fibre
texture is produced during processing, with the c-axis of the Bi2223 plates
parallel to the tape normal direction. Quantitative analysis suggests that
the orientation density along the fibre texture is close to random. In
contrast the distribution of misorientations shows significant correlations
between the orientations, and is skewed towards low misorientation angles. A
more detailed investigation reveals that the structure consists of colonies
of plates, with low angle misorientations within each colony. Analysis of
the rotation axes shows some differences as a function of misorientation
angle.
88.
Godfrey, A., W. Q. Cao, et al. (2005). "Stored Energy, Microstructure,
and Flow Stress of Deformed Metals." Metallurgical and Materials
Transactions A 36A(9): 2371-2378.
The stored energy of plastic deformation has been estimated from
transmission electron microscope measurements of dislocation boundary
spacings and misorientation angles using Al (99.99 pct) cold rolled to
reductions of 5 to 90 pct as an example system. In order to obtain the most
accurate estimate of stored energy, it is necessary to take into account the
presence of two classes of dislocation boundary, considering the boundary
misorientation angle distribution and the stereology of each class
independently. Stereological relationships are developed to predict the
stored energy estimates that would result from electron backscatter pattern
(EBSP) investigations on these microstructures. The calculations show that
EBSP investigations can be used to estimate the stored energy, but that at
low strains, the limited angular resolution will lead to a significant
underestimation. A relationship between the flow stress (0.2 pct offset) and
the stored energy is found, though the relationship differs significantly
for the low and high strain regimes. At low strains, the flow stress is
linearly related to the square root of the stored energy (ES)
according to Σ -Σ0 = Ma
[(G/K)ES]0.5, where G is the bulk modulus, M is the
Taylor factor, and K and α are constants.
89.
Godfrey, A., Y. B. Zhang, et al. (2004). Monte Carlo simulation of
cube-texture evolution during grain growth of high-purity nickel. The Fifth
Pacific Rim International Conference on Advanced Materials and Processing,
Baijing, China, Trans Tech Publications Ltd.
A Monte Carlo Potts model has been used to investigate cube-texture
strengthening during grain growth in rolled high-purity Ni-tapes. The
initial conditions for the simulations have been taken from electron
back-scatter pattern (EBSP) orientation maps of already fully recrystallized
samples. Experimentally, grain growth leads to an increase in the cube
volume fraction to > 95%, accompanied by an approximately ten-fold
increase in the grain size. High cube volume fractions can be predicted
under a number of conditions, though a small surface energy advantage of
just 2% for cube-oriented grains is required to match the texture
strengthening to the grain size change. An additional issue of interest is
the influence on the grain growth of the large area-fraction of twin
boundaries in the fully recrystallized condition. The presence of boundaries
with low energy has a strong influence on the simulated microstructural
evolution. (Application: substrates for YBCO superconductors.)
90.
Goehner, R. P. and J. R. Michael (1996). "Phase Identification in a
Scanning Electron Microscope Using Electron Backscattered Kikuchi
Patterns." Journal of Research of the National Institute of Standards
& Technology 101(3): 301-308.
91.
Goehner, R. P., J. R. Michael, et al. (1992). Analysis of SEM Electron
Backscattered Kikuchi Patterns Using a CCD Detector And A Macintosh
Computer. The 50th Annual Meeting of the Electron Microscopy Society of
America, San Francisco, San Francisco Press.
92.
Goehner, R. P., J. R. Michael, et al. (1992). Slow-Scan CCD Observation of
Backscattering Patterns in SEM. 50th Annual Meeting of the Electron
Microscopy Society of America, San Francisco Press.
93.
Gomez, X. and J. Echeberria (2003). "Microstructure and mechanical
properties of carbon steel A210-superalloy Sanicro 28 bimetallic
tubes." Materials Science and Engineering A 348(1-2): 180-191.
The viability by hot co-extrusion of a new bimetallic tube: carbon
steel A-210-G deg A1/iron based superalloy Sanicro 28 (UNS N08028) both by
hot torsion tests and by diffusion bonding experiments using hipping has
been verified. An excellent metallurgical bond was obtained after the
industrial hot co-extrusion process. Both the interdiffusion of the elements
across the interface, and the microstructure have been analysed by optical
microscopy, SEM, TEM and EBSD (electron backscattered diffraction). On the
Sanicro 28 side a profuse precipitation of Cr/Mo carbides was found in the
region close to the interface. In the hipped specimens and in the
heat-treated bimetallic tubes, as result of the nickel and chromium
diffusion from the superalloy to the carbon steel, austenite and martensite
sub-bands were observed parallel to the interface on the steel side. The
optimum heat treatment performed on the bimetallic tubes consisted of an
austenitising-solution treatment at 1100 deg C, and a stabilisation
annealing at 900 deg C, followed by air cooling.
94.
Gomoyunova, M. V., I. I. Pronin, et al. (1999). "Kikuchi-Band Formation
in Medium-Energy Electron-Diffraction Patterns." Physics of theSolid
State 41(3): 369-374.
95.
Goran, D., J.-J. Fundenberger, et al. (2004). Pure Ni single crystal of cube
orientation deformed by equal channel angular extrusion. 2nd International
Conference on Texture and Anisotropy of Polycrystals (ITAP 2), Metz, France,
Balaban Publishers; Scitec Publications.
Texture and microstructure were investigated after 1 pass equal
channel angular extrusion (ECAE) of a single crystal cube oriented Ni
billet. Neutron and X-ray diffraction were used to determine global and
local textures, respectively. To investigate the fine scale microstructural
features EBSD was used. Substantial variations in texture and microstructure
resulting from different efficiencies in the shearing process were locally
recorded through the billet height.
96.
Goran, D., J.-J. Fundenberger, et al. (2005). Heterogeneity of deformation
in pure Ni single crystal of cube orientation deformed by equal channel
angular extrusion. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans
Tech Publications.
Texture and microstructure were investigated after 1 pass equal
channel angular extrusion (ECAE) of a single crystal cube oriented Ni
billet. Neutron and X-ray diffraction were used to determine global and
local textures, respectively. EBSD and TEM investigations were also carried
out in order to study fine scale microstructural features. Substantial
variations in texture and microstructure, resulting from different
efficiencies in the shearing process, were locally recorded through the
billet height. The deformation was heterogeneous on both micro and macro
scales.
97.
Gordin, D. M., T. Gloriant, et al. (2005). "Characterization of a
laser-nitrided titanium alloy by electron backscattered diffraction and
electron probe microanalysis." Surface and Interface Analysis
37(13): 1161-1167.
After a laser gas nitriding treatment of the Ti-7.5Al (atom%)
titanium-based alloy, we used a combination of electron backscattered
diffraction (EBSD) in scanning electron microscope and electron probe
microanalysis (EPMA) techniques in order to efficiently characterize the
different phases in the resolidified layer. Representative measurements of
chemical composition and reliable determination of crystal structure were
possible for each phase of the complex microstructure. The reaction zone is
formed by a mixture of isostructural TiN phases with dendritic and/or
'coarse' needles morphology, fixed into a α-Ti matrix (martensite)
with a thin needle aspect. The nitrogen solubility was found to remain very
low in the α-Ti matrix (up to 2-3 atom %), while in the TiN phase, an
aluminum solubility as high as 4 atom % was measured, reducing drastically
the nitrogen content into a Ti79N17Al4
chemical composition.
98.
Gottstein, G. (2002). Evolution of Recrystallization Textures - Classical
Approaches and Recent Advances. ICOTOM 13, Seoul, Korea, Trans Tech
Publications Inc.
The current state of understanding of recrystallization texture
development and of recrystallization texture modeling and prediction is
reviewed. It is demonstrated that classical approaches as well as current
models can only explain measured textures but fail to reliably predict
textures. The strengths and deficiencies of major developments are
discussed. We demonstrate that the interdependency of a correct growth law
and an appropriate nonrandom nucleus texture effectively controls the
emergence or suppression of recrystallization texture components. Without
deeper insight into these fundamental microstructural proceeses a
quantitative texture prediction is bound to fail no matter how sophisticated
the used approach. In essence, we do not need better recrystallization
models, we need better models and data of nucleation and growth.
99.
Gottstein, G. and O. Engler (1993). "Local texture measurements with
the scanning electron-microscope." Journal de Physique IV 3(C7):
2137-2142.
Techniques for convenient measurement of the crystallographic
orientation of small volumes in bulk samples by electron diffraction in the
SEM are discussed. They make use of Selected Area Electron Channelling
Patterns (SAECP) and Electron Back Scattering Patterns (EBSP). The principle
of pattern formation as well as measuring and evaluation procedure are
introduced. The methods offer a viable procedure for obtaining information
on the spatial arrangement of orientations, i.e. on orientation topography.
Thus, they provide a new level of information on crystallographic texture.
An application of the techniques for local texture measurements is
demonstrated by an example, namely for investigation of considering the
recrystallization behavior of binary Al-1.3% Mn with large precipitates.
Finally, further developments of the EBSP technique are addressed. (Author
abstract) [References: 18]
100.
Gottstein, G. and T. A. Samman (2005). Texture Development in pure Mg and Mg
Alloy AZ31. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech
Publications.
Texture evolution in pure Mg and Mg alloy AZ31 during deformation
and annealing was investigated. The poor low temperature ductility can be
attributed to both, insufficient shear systems and unfavorable deformation
geometry. Static recrystallization was shown to proceed discontinuously
despite little texture change. High temperature deformation was accompanied
by dynamic recrystallization with similar texture development as during
static recrystallization.
101.
Gottstein, G., M. Crumbach, et al. (2005). Recrystallization and
Transformation Textures. Solid to Solid Phase Transformations in Inorganic
Materials 2005, Phoenix, Arizona, USA, TMS.
The evolution of crsytallographic texture during recrystallization
and diffusion controlled phase transformations is inttroduced and compared.
It is shown that the α-γ transformation texture in a
microalloyed steel is primarily determined by unbalanced selection of
Kurdjimov-Sachs variants. In contrast, for texture formation during
recrystallization both nucleation and growth play an essential role. For a
successful prediction of recrystallization textures, the nucleation texture
as well as the relative growth rate are necessary model ingredients.
Although recrystallization and diffusional phase transformations proceed by
nucleation and growth and develop sharp textures, the physics of texture
formation in both processes is very different.
102.
Gourgues, A.-F. (2002). "Overview: Electron backscatter diffraction and
cracking." Materials Science and Technology 18: 119-133.
Electron backscatter diffraction (EBSD) is now a well developed
technique that allows for determination of `microtexture’, i.e.
texture at the scale of the grain size. The effect of the local
crystallographic properties on microscopic and macroscopic cracking
resistance was studied in a large number of materials. Electron backscatter
diffraction and EBSD related techniques provide a lot of data concerning
intergranular, brittle transgranular, and fatigue cracking. In particular,
they help with understanding the role of the grain boundary structure, the
grain orientation and the misorientation between grains respectively.
Electron backscatter diffraction characterisation of interfaces has already
led to improvements of material performance in practical industrial
applications, a typical example being given by grain boundary engineering.
Information about the local crystallography together with a high spatial
resolution encourages the application of the technique to cracking modes of
other materials such as ceramics. Moreover, EBSD data can be of great
relevance in micromechanical modelling of properties of polycrystalline
materials.
103.
Gourgues, A.-F. (2003). Microstructure induced by the bainitic
transformation in steels during welding: effect on the resistance to
cleavage cracking. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech
Publications Ltd.
Electron backscatter diffraction (EBSD) is used to investigate the
crystallographic properties of bainitic and martensitic microstructures
obtained after rapid thermal cycles. Numerous low angle boundaries are found
within upper bainite packets, which are in fact sets of finely interlocked
groups of variants. Lower bainitic packets contain many high angle
boundaries. Micromechanical modelling suggests that self-accommodation of
the phase transformation induced strain is more efficient for lower bainite
than for upper bainite. Moreover, the fine structure of lower bainite does
not necessarily induce high impact toughness properties, owing to the
complex three-dimensional shape of the group of laths.
104.
Gourgues, A.-F., H. M. Flower, et al. (2000). "Electron Backscattering
Diffraction Study of Acicular Ferrite, Bainite and Martensite Steel
Microstructures." Materials Science and Technology 16(1): 26-40.
This study deals with acicular ferrite, bainite, and martensite
microstructures observed in three low alloy steels. Electron backscattering
diffraction (EBSD) was used to assess crystallographic features of these
microstructures. In each area studied by EBSD mapping,
‘crystallographic packets’ defined as clusters of points sharing
the same crystallographic orientation were compared with
‘morphological packets’ observed in the corresponding light
micrograph. Microtexture studies suggested that acicular ferrite and upper
bainite grow with Nishiyama– Wassermann relationships with the parent
austenite phase, whereas lower bainite and martensite consist of highly
intricate packets having Kurdjumov–Sachs relationships with the parent
phase. In all cases three highly misoriented texture components were found
within each former austenite grain. Electron backscattering diffraction also
gave information about the cleavage and intergranular reverse temper
embrittlement fracture mechanisms of these steels. In conclusion, it is
shown that EBSD is a powerful tool for studying phase transformation and
fracture mechanisms in steels on a microscopic scale.
105.
Goussery, V., Y. Bienvenu, et al. (2004). "Grain size effects on the
mechanical behavior of open-cell nickel foams." Advanced Engineering
Materials (Germany) 6(6): 432-439.
The dependence of the mechanical behavior of nickel foams upon their
grain size was studied. First, the grain coarsening phenomenon which occurs
during the processing of foams was analyzed. A metallurgical
characterization of the grain growth during heat treatment was performed.
The grain size effects on the mechanical properties was then studied,
namely, via the Hall-Petch law. The foam walls being very thin, roughly 10
µm in thickness, grain growth and mechanical behavior might be
different compared with conventional materials. The present results obtained
with foams were compared with literature data on bulk pure nickel and with
nickel foils of 10 and 50 µm in thickness which are good candidates
for the modeling of the cell walls. The EBSD technique allowed observing the
absence of preferred crystallographic orientations for both foams and foils.
A mechanical model in the spirit of that by Gibson and Ashby was finally
presented incorporating the grain size effect on yield strength and
hardening modulus. This model provided a good estimation of the experimental
data.
106.
Goyal, A. (2000). Grain Boundary Character Based Design of Polycrystalline
High Temperature Superconducting Wires. Electron Backscatter Diffraction in
Materials Science. A. J. Schwartz, M. Kumar and B. L. Adams. New York,
Kluwer Academic/Plenum Publishers: 299-314.
107.
Goyal, A., E. D. Specht, et al. (1994). "Grain Boundary Misorientations
and Percolative Paths in High Jc Powder in tube (BiPb)2Sr3Ca3Cu3Ox."
Applied Physics Letters.
108.
Goyal, A., E. D. Specht, et al. (1995). "Microtexture and Mesotexture
in High-J(C) Bi-2223." Journal of Electronic Materials 24(12):
1865-1868.
109.
Goyal, A., E. D. Specht, et al. (1995). "Formation of Colonies of
Locally Aligned Grains During Thallination of Spray-Pyrolyzed
Ba2Ca2Cu3OxThick Films."
IEEE Transactions On Applied Superconductivity 5(2):
1950-1953.
110.
Goyal, A., E. D. Specht, et al. (1997). Texture and Grain Boundaries in
Epitaxial Oxide Multilayers including Superconductors, on Biaxially Textured
Metal Substrates. Microscopy and Microanalysis, Cleveland, Ohio,
Springer.
111.
Goyal, A., E. D. Specht, et al. (1997). Analysis of Multiphase Materials
Using Electron Backscatter Diffraction. Microscopy and Microanalysis 1997,
Cleveland, Ohio, Springer.
112.
Goyal, A., E. D. Specht, et al. (1997). "Grain Boundary Studies of
High-Temperature Superconducting Materials Using Electron Backscatter
Kikuchi Diffraction." Ultramicroscopy 67: 35-37.
113.
Goyal, A., R. Freenstra, et al. (1999). Texture development,
recrystallization, and transference of texture between ceramic multilayers,
epitaxially grown on rolling assisted biaxially textured substrates
(RABiTS). Twelfth International Conference on Textures of Materials (ICOTOM
12), McGill University, Montreal, Canada, NRC Research Press.
114.
Grabke, H. J., B. Huning, et al. (2005). "Annealing of Fe-15at.%Cr
alloy in N2-H2 gas mixtures: Effect of hydrogen."
Diffusion and Defect Data. Pt A Defect and Diffusion Forum
237-240(Part II): 928-933.
The effect of hydrogen during annealing of Fe-15.at%Cr alloy on the
diffusion profile was investigated concerning the enrichment of chromium and
the selective oxidation. Samples were exposed to an annealing gas mixture
with different hydrogen contents in an infrared heating furnace and heated
to 800r indicat C, kept for 60 seconds and then cooled down to room
temperature. After the experiments, field emission scanning electron
microscopy (FE-SEM) equipped with electron back-scattering diffraction
(EBSD) and x-ray photoelectron spectroscopy (XPS) were employed to
characterize the morphology, elemental depth profiles and the chemical
states of the elements. The annealing increased the Cr content at the
surface in all atmospheres. The increase of hydrogen content in the
atmosphere further increased the Cr to Fe ratio in near-surface, and the
thickness of the layer affected by the heat treatment. The selective
oxidation of chromium occurred as internal Cr2O3
formation, as a function of the Cr content, rather than the oxygen partial
pressure. Hydrogen facilitated the diffusion of chromium probably by
cleaning of fast diffusion paths.
115.
Grabski, M. W. (1985). "Mechanical-Properties of Internal
Interfaces." Journal de Physique I 46(NC-4): 567-579.
116.
Grabski, M. W. (1988). "Mobility of Dislocations in
Grain-Boundaries." Journal de Physique I 49(NC-5):
497-506.
117.
Grabski, M. W. and J. W. Wyrzykowski (1980). "The Effect of the
Spreading of Grain-Boundary Dislocations on the Tensile Behavior of a
Fine-Grained Austenitic Steel at High-Temperatures." Materials Science
and Engineering 44(2): 229-237.
118.
Grant, E., D. J. Jensen, et al. (1986). "A Determination of the Texture
of a Directionally Solidified Sample of High-Purity Copper." Journal of
Materials Science 21(5): 1688-1692.
119.
Gray III, G. T., G. C. Kaschner, et al. (1999). "The influence of
interstitial content, temperature, and strain rate on deformation twin
formation." Advances in Twinning. Proceedings International Symposium.
In this paper, examples of the influence of oxygen content,
temperature, texture, and strain rate on the mechanical behavior and
propensity for deformation twin formation in two grades of alpha -titanium
and alpha -zirconium are presented. The influence of strain rate,
temperature, and deformation on the mechanical response and twin formation
of high-purity (low-interstitial) and lower-purity (higher-oxygen-content)
Ti and Zr were probed utilizing quasi-static, Split-Hopkinson-Bar, and
plate-impact (shock) loading. Suppression of deformation twin formation in
the high-oxygen content Ti and Zr is seen to simultaneously correlate with
higher yield strengths and lower stage-II work-hardening rates. The
influence of interstitial content on the kinetics of twin formation and work
hardening is contrasted in light of previous literature studies. The use of
automated electron backscatter diffraction (EBSD) analysis to quantify
specific twin system activation and twin morphology as a function of the
imposed temperature and strain rate of deformation is discussed. The
influence of deformation twinning on the overall mechanical behavior and
constitutive modeling description of low-symmetry metals and alloys is
discussed. Topics include: (1) the microstructural and experimental
variables influencing twin formation in Ti and Zr and twinning topics
related to high-strain-rate loading, and (2) the influence of deformation
twinning on the constitutive response of low-symmetry metals and alloys. (39
References).
120.
Gray III, G. T., S. I. Wright, et al. (1996). Influence of large-strain
deformation on the microstructure, texture and mechanical response of
tantalum bar. Tantalum. E. Chen, A. Crowson, E. Lavernia, W. Ebihara and P.
Kumar. Wartrendale, PA, The Minerals, Metals & Materials Society:
239-248.
121.
Gray III, G. T., S. R. Bingert, et al. (1994). "Influence of Tungsten
Alloying Additions on the Mechanical Properties and Texture of
Tantalum." Materials Research Society Symposium Proceedings 322:
407-12.
122.
Greiser, J., D. Muller, et al. (1999). "Growth of Giant Grains in
Silver Thin-Films." Scripta Materialia 41(7): 709-714.
123.
Greiser, J., P. Mullner, et al. (1998). Orientationally resolved grain size
distributions in thin films. Texture and Anisotropy of Polycrystals.
Zurich-Uetikon, Transtec Publications Ltd. 273-2: 237-242.
We study the grain structure of thin films in two dimensions. The
grain structure is analyzed in terms of grain size and orientation, by means
of electron backscattering diffraction (EBSD). We propose the line scan
method for the efficient acquisition of data and define appropiate
quantities for the description of the microstructure. These concepts are
applied to a nickel thin film. The texture of this film is found to have
three components (< 111 >, < 100 >, and random). The grain size
distribution is bimodal where the large grains are all in < 100 >
orientation. It is shown that the separation of grain size and grain
orientation allows a more complete characterization of grain structures and
reveals information not visible in conventional grain size
distributions.
124.
Greiser, J., P. Mullner, et al. (2001). "Abnormal Growth of Giant
Grains in Silver Thin-Films." Acta Materialia 49(6): 1041-1050.
Abnormal growth of "giant" grains in the millimeter range
was observed in silver thin films with thicknesses of 2.0 and 2.4 μm.
The effect depends on deposition temperature and deposition geometry. The
microstructure and texture of as-deposited and annealed films have been
characterized using X-ray, electron backscatter diffraction (EBSD) and
focused ion beam (FIB) techniques. Abnormal grain growth is found whenever a
special texture is formed during film deposition. Otherwise normal grain
growth occurs. The texture type—and thus the grain growth
mode—can be controlled by adjusting the process parameters. During
abnormal grain growth, the initial (111) texture transforms completely into
001. Growth of 111-oriented grains stagnates at a size smaller than the film
thickness with a non-columnar grain structure. This stagnation promotes
orientation-selective growth of 001 grains.
125.
Griesshaber, E., W. Schmahl, et al. (2004). Microstructure of brachiopod
shells - an inorganic/organic fibre composite with nanocrystalline
protective layer. Mechanical Properties of Bioinspired and Biological
Materials. Symposium, Boston, Massachusetts, USA, Materials Research
Society, Warrendale, PA, USA.
We investigated the ultrastructure of the modern calcitic
brachiopods Megerlia truncata (Linnaeus) and Terebratalia transversa
(Sowerby) with SEM, electron backscattering diffraction and microhardness
indentation. The outer, primary shell layer can be regarded as a
nanocrystalline thin film that forms a hard protective coating around the
inner, much softer secondary layer that can be expressed as an
inorganic/organic fibre composite. The fibrous, curved growth of the
secondary shell layer crystals occurs in arbitrary directions perpendicular
to the <0 0 0 1> triad symmetry direction of calcite and is most
likely obtained by simple confinement to a protein sheath rather than by
biomolecular adsorbates blocking growth of any specific crystal face. The
curvature of the fibres is caused by rearrangements of the secreting cell
array during growth, whereby the existing crystal lattice is not distorted.
It serves as a substrate for continued crystal growth. Thus biologically
mediated calcite crystallization is a purposeful process and seems to be
significantly different to the inorganic crystallization of calcite.
126.
Groeber, M., B. Haley, et al. (2004). Microstructural Characterization Using
3-D Orientation Data Collected by an Automated FIB-EBSD System. Materials
Processing and Design: Modeling, Simulation and Application Proceedings of
NUMIFORM, Columbus, Ohio, USA, AIP.
In this work, a new technique utilizing an automated approach of
combining a Focused Ion Beam (FIB) and Electron Back-Scatter Diffraction
(EBSD) system was implemented for the collection of 3-D orientation data
that can be used to more accurately model grain and sub-grain particle
structures. The process is currently capable of sectioning a sample with
inter-slice thicknesses as low as 100 nanometers and capturing an
orientation map of each slice. Automation of this technique allowed for
rapid data collection with the ability to update settings in real time. The
orientation data obtained by the EBSD scans consists of each grid
point’s position, three Euler angles and phase. Reconstruction of the
3-D orientation data involves combining or “stacking” the 2-D
slices obtained by the FIB-EBSD process. The orientation data of each slice
is combined into one data file containing orientation information for each
point on the 3-D grid, which can have spacing as little as 100 nanometers in
all three directions. A program developed in this work, Micro-Mesher, uses
the reconstructed orientation information to define microstructural features
such as grains and second phase particles. Micro- Mesher constructs grain
boundaries with line and plane segments using an error per unit length
approach to approximate the complex grain boundaries. Important
microstructural statistics that are used to define and characterize the 3-D
microstructure are also calculated by Micro-Mesher. Such important
parameters include: grain size, no. f neighboring grains, orientations and
misorientations, second phase particles size and inter particle spacing as
well as others. The 3-D statistical information gained from this process
improves the ability to accurately characterize the microstructure.
127.
Grossin, D., C. Henrist, et al. (2006). "EBSD study on YBCO textured
bulk samples: correlation between crystal growth and `microtexture'."
Superconductor Science & Technology 19(2): 190-199.
This work describes an electron backscattered diffraction (EBSD)
study of the perovskite-derived structures
YBa2Cu3O7-δ. After having
pointed out the difficulties of EBSD analyses in resolving the orientations
of these pseudo-cubic structures, various YBaCuO bulk samples are analysed
and the correlation between the microstructure, crystal growth and global
texture, determined by neutron diffraction, is carried out. Homogeneous
`microtexture' with small subdomain misorientation of 12 degrees are
measured for YBCO top seeding melt textured growth (TSMTG) samples. YBCO
perforated samples also exhibit misoriented subdomains, giving rise to a
heterogeneous `microtexture' correlated to the YBCO growth front and to the
pattern used for the perforating.
128.
Guessasma, S., E. Suzon, et al. (2004). Static Recrystallization of FeAl in
the Presence of Second Phase Particles: Experimental and Modeling
Investigations. Second Joint International Conference on Recrystallization
and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech
Publications Ltd.
129.
Guezou, G.-C., T. Baudin, et al. (2000). Application of Experimental and
Numerical Techniques to Study Correlations between Texture,
Microstructure and Mechanical Properties of a Geomaterial. Thermec
2000, Las Vegas, Nevada, USA, Elsevier Science Ltd.
Quartzites are nearly monomineral rocks, very common in the upper
crust of the earth. Due to the difficulty in performing direct experiments,
microstructures and textures have been empirically explained in connection
with macroscopic deformation features and widely used in geological
kinematics studies. Experimental and numerical approaches have been applied
to better understand the deformation path recorded by a rock pile lying in
the core of the Betic mountain belt (Spain). For the purpose, a set of
samples has been collected and both microstructures and textures (by neutron
diffraction) have been characterized. The most frequent components have then
been connected with an approximate ratio of deformed and recrystallized
areas observed in the corresponding microstructures. The latter correlation
between microstructure and texture has been tentatively performed by
comparing the results published in the geological literature, but also with
the texture of hexagonal titanium or zirconium alloys and with the help of
Electron Back Scattered Diffraction measurements. To improve the simulation
of the natural deformation textures, residual elastic strain tensors have
been estimated by neutron diffraction. Then, to consider the effect of
static recrystallization on both microstructures and textures, the
experimental/numerical coupling initially applied to simulate the formation
of the cube component during primary recrystallization in Fe36%Ni alloys or
to simulate the abnormal growth of Goss grains in Fe3%Si alloys has been
extended to quartzites. This approach consists in a Monte Carlo simulation
that uses as experimental input data, the initial microstructure and the
corresponding microtexture determined either by Orientation Imaging
Microscopy or by Transmission Electron Microscopy.
130.
Gui, J. N., J. B. Wang, et al. (2001). "On Some Discrepancies in the
Literature About the Formation of Icosahedral Quasi-Crystal in Al-Cu-Fe
Alloys." Journal of Materials Research 16(4): 1037-1046.
To clarify some discrepancies in the literature about the formation
of icosahedral quasi-crystal (IQC) in Al-Cu-Fe alloys, microstructures and
constituent phases of Al62.5Cu25Fe12.5 and
Al65Cu20Fe15 alloys were studied. Each
dendritic arm of the primarily solidified
λ-Al13Fe4 phase is a single crystal that
possesses no definite orientation relationship with the IQC, formed by
peritectic reaction (L + l + β >> IQC) or a solid-state reaction
(Cu-rich phases + l + β >> IQC). This fact disproves an
assumption that l-phase is an approximant of the IQC. Two types of cubic
phase, β-phase with CsCl structure containing more Fe and
θ3phase, which is a supersdtructure and contains less Fe,
were observed depending on the composition and thermal history of the
samples.
131.
Guiglionda, G., A. Borbely, et al. (2004). "Orientation-dependent
stored energies in hot deformed Al-2.5%Mg and their influence on
recrystallization." Acta Materialia 52(12): 3414-3423.
The dislocation densities in individual texture components of a hot,
plane strain compressed, Al-2.5%Mg alloy have been determined by high
resolution X-ray diffraction using recent methods for peak broadening
interpretation. After deformation at 400 deg C and strains up to 1.5
dislocation densities range from 2 to 20 x 1013 m-2. Both high energy
synchrotron (European synchrotron radiation facility, ESRF) transmission
peak analysis and standard reflection line analysis show that the S
{123}<412> component develops significantly higher stored energies
than the cube, brass {011}<211> and Goss {011}<100> components.
After subsequent annealing to partial recrystallization, EBSD orientation
maps over large areas demonstrate that the high energy S component is
preferentially consumed by recrystallization. It is also shown that the
development of the cube recrystallization texture is due to a nucleation
frequency advantage, function of the applied strain.
132.
Guilmeau, E., C. Henrist, et al. (2005). Texture of Alumina by neutron
diffraction and SEM-EBSD. Textures of Materials - ICOTOM 14, Leuven,
Belgium, Trans Tech Publications.
The orientation distributions of α-Al2O3 textured ceramics are
determined from neutron diffraction and SEM-EBSD. A curved
position-sensitive detector coupled to a tilt angle (χ) scan allowed
the whole neutron diffraction pattern treatment in the combined
Rietveld-WIMV-Popa algorithm. Analyses from neutron and electron diffraction
data gave similar results if EBSD data are smoothed to account for grain
statistics. Four textured alumina ceramics were prepared by slipcasting
under a high magnetic field and sintered at 800°C, 1300°C,
1400°C and 1600°C. The inverse pole figures and EBSD-mapping
highlights the influence of the magnetic field and sintering temperature on
the texture development. The inverse pole figures calculated for the fiber
direction show a major (001) component for all the samples. With the
increasing sintering temperature, the texture strength is enhanced and the
c-axis distribution is sharper. The effectiveness of the combined approach
for determining the crystallite size is also evident. As a global trend, the
calculated crystallite size and observed grain size are similar and increase
with the increasing sintering temperature. The mechanism of the texture
development in the sintered specimens is certainly initiated from the
preferred orientation of the green body after slip-casting under a high
magnetic field. The basal texture is enhanced during sintering by selective
anisotropic grain growth. We evidenced here the powerfulness of the Rietveld
texture analysis correlated to SEM-EBSD calculation to provide a basis for
the correlation of texture, microstructural parameters and anisotropic
properties.
133.
Gulgun, M. A., M. L. Mulvihill, et al. (1998). Microstructure and
Microchemistry of Y-Doped α-Al2O3. Turkish
Ceram.Soc. IV, Eskisehir,Turkey.
The samples had a bimodal grain size distribution that was strongly
correlated to the frequency and distribution of Y3Al5O12 (YAG) precipitates
in the microstructure. Y segregated to most of the grain boundaries with a
nominal excess concentration of GAMMA=1.75+-0.5 atoms/nm2 at random
boundaries. Two types of twin boundaries did not accommodate any Y. None of
the boundaries or triple point junctions contained a glassy grain boundary
phase. Strong interaction of the grain boundaries and dislocations with YAG
precipitates indicated a pinning mechanism by the precipitates. Y doping did
not appear to favor formation of special boundaries in alpha-alumina. 11
refs.
134.
Gungor, A., K. Barmak, et al. (2002). "Cu and Dilute Binary Cu(Ti),
Cu(Sn) and Cu(Al) Thin Films: Texture, Grain Growth and Resistivity."
Materials Research Society Symposium Proceedings 721: J3.2.1 -
J3.2.6.
Annealing Cu and dilute Cu(Ti), Cu(Sn) and Cu(Al) alloy films
resulted in the strengthening of film texture, with the strongest
<111> fiber texture being found for Cu(Ti). Annealing also resulted in
a decrease of electrical resistivity and the growth of grains, with the
largest grain size and lowest resistivity being seen for pure Cu itself.
Among the alloy films, the lowest resistivity was found for Cu(Ti) and the
largest grain size for Cu (Al). Electron beam evaporated films with
compositions in the range of 2.0-3.0 at% and thicknesses in the range of
420-540 nm were annealed at 400°C for 5 hours. Four point probe
resistance measurement, xray diffraction and transmission electron
microscopy were used to follow the changes in film resistivity, texture and
grain size.
135.
Gunther, G. and P. J. Wilbrandt (1995). "The Determination of
Low-Energy Grain-Boundaries by the Spheres-on-Plate Experiment in Cu and
Cu-0.1 at-Percent Mn." Physica Status Solidi A 150(2):
635-651.
136.
Gunturi, S. S. K., D. W. MacLachlan, et al. (2000). "Anisotropic creep
in CMSX-4 in orientations distant from <001>." Materials Science
and Engineering A 289: 289-298.
Constant load creep tests have been performed on the single crystal
nickel base superalloy CMSX-4 in crystallographically unstable orientations
distant from the <001> pole of the standard stereographic triangle at
1023 K (750°C) and varying stress levels. Orientations distant from the
<001>–<111> boundary had high creep rates and relatively
low rupture lives, while the orientations closer to it had relatively low
initial creep rates and longer rupture lives. Electron back scatter
diffraction patterns, cross section shape change measurements on creep
tested specimens, and optical microscopy indicate that the operating slip
system is of the type {111}<112> in orientations far from the
<001>–<111> boundary. The results are explained based on
the resolved shear stress acting on the operating slip system taking into
consideration the rotations and changes in cross section. A theory based on
the ease of generation of superlattice intrinsic stacking faults is proposed
to account for the observed creep rates in various orientations. A finite
element model based on the slip system approach is used to demonstrate the
validity of the experimental results.
137.
Guo, H., K. Okuda, et al. (2000). "Surface relief of alpha "
martensite in a Ti-Mo alloy." Metallurgical and Materials Transactions
A 31A(3): 599-605.
The surface relief of alpha " martensite plates in a
polycrystalline Ti-4.74 at. pct Mo alloy was studied by atomic force
microscopy (AFM). The orientation of matrix grains was measured by electron
backscatter diffraction (EBSD), and measured surface tilt angles were
compared with calculation by the crystallographic theory of martensite
transformation. The observed maximum tilt angle was close to the predicted
value of 7.57 deg. The overall agreement between measured and calculated
tilt angles was improved significantly by taking into account not only the
inclination of habit plane to the specimen surface, but also the shear
direction predicted from the theory. The tilt angle may vary with the moving
direction of the interface unless the habit plane is perpendicular to the
specimen surface. However, this effect was small in this transformation. (29
References).
138.
Guo, Z., D. Solas, et al. (2003). Microstructural changes in copper
processed by Equal Channel Angular Extrusion and static annealing. Thermec'
2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.
Grain refinement of metallic materials may be achieved by imposing
severe plastic deformation through procedures such as Equal Channel Angular
Extrusion (ECAE). In this work, the development of the fine microstructure
in copper after 1, 4, and 8 passes was studied. Samples were obtained
through rotating billets through 90 degrees between each extrusion path
(route Bc). Transmission Electron Microscopy has been employed to measure
crystallographic orientations and to draw the corresponding color maps. The
thermal stability of the ultrafine grained copper manufactured by the ECAE
process was examined by imposing static annealing treatment of 200°C. At
this temperature, recrystallization is observed, but the recrystallized
grain size remains small (2 - 3 µm) even after long annealing
times.
139.
Gupta, P., H. Jain, et al. (2005). "Observation of ferroelectricity in
a confined crystallite using electron-backscattered diffraction and
piezoresponse force microscopy." Applied Physics Letters 87(17).
LaBGeO5 is a model transparent ferroelectric
glass-ceramic (TFGC) material, developed as an inexpensive alternative to
single-crystal nonlinear optical materials. The optical activity of the TFGC
originates from the ferroelectric phase which remains under a hydrostatic
pressure exerted by the surrounding glass matrix. A combination of two
techniques, electron-backscattered diffraction (EBSD) and piezoresponse
force microscopy (PFM), is employed to monitor the development of the
ferroelectric phase. A method is proposed to theoretically construct PFM
amplitude maps from EBSD orientation maps. The theoretical vertical
piezoresponse map is compared with the experimental piezoresponse map from
PFM. A good correlation between the theoretical and experimental maps is
observed.
140.
Gupta, S. P. and B. K. Prasad (1986). "The Effect of Thermal Cycling on
the Kinetics of Cellular-Phase Transformation in a Cu-in Alloy."
Materials Science and Engineering 77(1-2): 181-190.
141.
Guruswamy, S., P. Mungsantisuk, et al. (2005). Deformation Behavior and
Texture Development During the Thermomechanical Processing of Fe-15 At.% Ga
Alloys Containing NbC. Trends in Materials and Manufacturing Technologies
for Transportation Industries and Powder Metallurgy Research and Development
in the Transportation Industry as held at the 2005 TMS Annual Meeting, San
Francisco, CA, USA, Minerals, Metals and Materials Society (TMS),
184 Thorn Hill Road, Warrendale, PA USA 15086-7528.
Fe-Ga alloys exhibit large magnetostriction in the 001 direction,
and 001 oriented single crystals or 100 textured polycrystalline forms of
these alloys are therefore highly desirable for use in automotive sensors
and actuators. Textured polycrystalline alloys are preferred due to lower
cost and better room temperature mechanical properties. This paper examines
the feasibility of an inexpensive thermomechanical processing approach
involving a sequence of controlled hot rolling, two-stage warm rolling with
intermediate anneal, and texture anneal to obtain 001 texture in
polycrystalline (Fe-15 at.% Ga) alloys containing NbC. Roll forces during
each pass of the hot and warm rolling stages were measured to examine the
deformation behavior of the alloys. Textures evolution during different
stages of processing was examined using Orientation Imaging Microscopy to
identify conditions that favor 001 texture development. The results indicate
that FeGa alloys with a strong 001 texture can be obtained using an optimal
NbC content and thermomechanical process conditions.
142.
Gutierrez, I., D. Hernandez, et al. (2004). "Analysis of ferrite grain
growth mechanisms during γ-α transformation in a niobium alloyed
steel using EBSD." Materials Science and Engineering A 385(1-2):
83-90.
The austenite to ferrite phase transformation was studied in a
C-Mn-Nb steel after different hot deformation schedules, leading to deformed
and recrystallized austenite. The mechanisms of nucleation and growth of
ferrite grains were investigated by means of the electron back scattered
diffraction (EBSD) technique. The ferrite microstructures were characterised
in terms of the misorientation angles between ferrite grains and the
deviations from an ideal Kurdjumov-Sachs orientation relationship with the
austenite. The results show that the grain refinement produced by the
accumulation of the deformation in the austenite is limited to a certain
extent by the ferrite grain coarsening taking place behind the
transformation front. Both coalescence and normal grain growth have been
observed to contribute to this coarsening. Coalescence is enhanced as a
result of the variant selection taking place in transformation from a
recrystallized austenite. The accumulation of the deformation in the
austenite results in ferrite-ferrite boundaries of higher misorientation,
causing coalescence in this case to be less favoured, as compared with
normal grain growth. Copyright 2004 Elsevier B.V. All rights
reserved.
143.
Guvenilir, A., G. C. Butler, et al. (1998). "X-Ray Microbeam
Quantification of Grain Subdivision Acompanying Large Deformations of
Copper." Acta Materialia 46(18): 6599-6604.
This work reports the application of X-ray microbeam diffraction to
quantifying grain subdivision processes in copper. Polychromatic synchrotron
X-radiation was used to study samples in the as-received (low deformation)
and 100% torsion strained material. The large range of domain
disorientations (within individual grains) observed in the highly strained
material agrees with results on other f.c.c. materials obtained by electron
beam methods; it is not surprising, therefore, that models of texture
development which do not include this effect predict too rapid sharpening of
preferred orientation compared to experimental pole figures.
144.
Guyot, B. M. and N. L. Richards (2005). "A study on the effect of cold
rolling and annealing on special grain boundary fractions in
commercial-purity nickel." Materials Science and Engineering A
395: 87-97.
It has been known for decades that thermomechanical processing,
through cold working and annealing can effectively increase the fraction of
special low energy grain boundaries in many FCC metals. The focus of the
reported work was to study the effects of cold rolling and annealing
processing parameters on both the fraction of special boundaries and the
random boundary connectivity in commercially pure nickel. It was found that
by using relatively low strain levels combined with high temperature
anneals, it was possible to increase the fraction of special boundaries to
65% and severely fragment the random boundary connectivity.
145.
Guyot, B., S.-L. Lee, et al. (2005). "Effect of small strain levels on
special boundary distribution in commercially pure nickel." Journal of
Materials Engineering and Performance 14(1): 85-90.
Commercially pure nickel has been processed via low-strain and
high-strain routes using various thermomechanical cycles with isochronal
annealing from 500 to 900 DGC. Electron backscattered diffraction was used
to characterize the percentage of special boundaries (Σ3-29) formed.
Measurements also included twin variants based on Σ3". Of the
various single-strain and multiple-strain temperature combinations that were
processed, both routes showed that a single low strain of about 2 to 6%
followed by annealing at 900 DGC for 10 min resulted in a doubling of the
special fraction of grain boundaries. In addition, the Σ3"
variants were also approximately doubled without the recourse to multiple
processing and/or multiple heat treatments. It was proposed, based on
theories from the literature, that extrinsic grain boundary dislocations
formed at low strain levels in a mantle-core formation and, on annealing,
climbed along the boundary and formed special grain boundary types.
145 records found
|
|
|
