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73 records found
1.
Vagin, N. P., A. A. Ionin, et al. (2004). "Pulsed electron-beam-sustained discharge in oxygen-containing gas mixtures: electrical characteristics, spectroscopy, and singlet oxygen yield." Quantum Electronics 34(9): 865-870.
The electrical and spectroscopic characteristics of electron-beam-sustained discharge (EBSD) in oxygen and oxygen-containing gas mixtures are studied experimentally under gas pressures up to 100 Torr in a large excitation volume (18 L). It is shown that the EBSD in pure oxygen and its mixtures with inert gases is unstable and is characterised by a small specific energy contribution. The addition of small amounts (1% - 10%) of carbon monoxide or hydrogen to oxygen or its mixtures with inert gases considerably improves the stability of the discharge, while the specific energy contribution W increases by more then an order of magnitude, achieving. 6.5 kJL-1atm-1 per molecular component of the gas mixture. A part of the energy supplied to the EBSD is spent to excite vibrational levels of molecular additives. This was demonstrated experimentally by the initiation of a CO laser based on the O2:Ar:CO = 1:1:0.1 mixture. Experimental results on spectroscopy of the excited electronic states O2(a1 Deltag) and O2(b3 Sigmag+), of oxygen formed in the EBSD are presented. A technique was worked out for measuring the concentration of singlet oxygen in the O2(a1 Deltag) state in the afterglow of the pulsed EBSD by comparing with the radiation intensity of singlet oxygen of a given concentration produced in a chemical generator. Preliminary measurements of the singlet-oxygen yield in the EBSD show that its value. 3% for W. 1.0 kJL-1atm-1 is in agreement with the theoretical estimate. Theoretical calculations performed for W. 6.5 kJL-1atm-1 at a fixed temperature show that the singlet-oxygen yield may be. 20%, which is higher than the value required to achieve the lasing threshold in an oxygen-iodine laser at room temperature.
2.
Vaillant, M. L., T. Gloriant, et al. (2003). "Partial crystallization of as-quenched Zr55Cu30Al10Ni5 bulk metallic glass induced by oxygen." Scripta Materialia 49: 1139-1143.
Dendritic crystals, randomly distributed into the as-quenched Zr55Cu30Al10Ni5 bulk metallic glass were characterized by optical microscopy, electron probe microanalysis, X-ray diffraction and electron backscattering diffraction. Oxygen enrichment is observed into these crystallites (formula: Zr7Cu4Al3O, space group: Fd3m, cell parameter: 5.70 Å) demonstrating the negative effect of oxygen, inducing partial crystallization during casting.
3.
Vale, S. H. (1988). "Instrumentation for Electron Back Scattering Pattern-Analysis." Institute of Physics Conference Series(93): 235-236.
4.
Valette, S., E. Audouard, et al. (2005). "Heat affected zone in aluminum single crystals submitted to femtosecond laser irradiations." Applied Surface Science 239(3-4): 381-386.
An experimental procedure is developed to quantify the radial dimension of the heat affected zone (HAZ) in metals submitted to laser pulses. A cube oriented aluminum single crystal is highly deformed by plane strain compression, then micro-drilled by 200 fs or 8 ns laser pulses, and finally analyzed by the electron back scattering diffraction technique. Recrystallized and recovered zones are observed as signatures of the HAZ. A typical value of 1.5 p.m is found in the femtosecond regime of illumination, whereas for nanosecond pulses a value of 25 mum is measured. These results are in accordance with previous experiments and numerical simulations.
5.
Valiev, R. Z. and T. G. Langdon (1993). "An Investigation of the Role of Intragranular Dislocation Strain in the Superplastic Pb-62-Percent Sn Eutectic Alloy." Acta Metallurgica et Materialia 41(3): 949-954.
6.
Valiev, R. Z., V. Y. Gerchman, et al. (1980). "On the Nature of Grain-Boundary Structure Recovery." Physica Status Solidi A 61(2): K95.
7.
Valiev, R. Z., V. Y. Gertsman, et al. (1983). "The Role of Non-Equilibrium Grain-Boundary Structure in Strain Induced Grain-Boundary Migration (Recrystallization After Small Strains)." Scripta Metallurgica 17(7): 853-856.
8.
Valiev, R. Z., V. Y. Gertsman, et al. (1983). "Study of Grain-Boundary Structure Changes During Recrystallization of Magnesium Alloy After Weak Deformations." Fizika Metallov I Metallovedenie 55(3): 554-558.
9.
Valiev, R. Z., V. Y. Gertsman, et al. (1983). "Non-Equilibrium State and Recovery of Grain-Boundary Structure.1. General Analysis, Crystallageometrical Aspects." Physica Status Solidi A 77(1): 97-105.
10.
Valiev, R. Z., V. Y. Gertsman, et al. (1986). "Grain-Boundary Structure and Properties Under External Influences." Physica Status Solidi A 97(1): 11-56.
11.
Valiyev, R. Z., O. A. Kaybyshev, et al. (1987). "Study of Grain-Boundary Gliding Simultaneous with Intra-Grain Gliding During Deformation of Zinc Bicrystals." Fizika Metallov I Metallovedenie 63(2): 396-401.
12.
Valle, R., S. van der Zwaag, et al. (2002). Influence of the Strain Path in Torsion on the Deformation and Recrystallization Textures of AA1050 and AA3103 Aluminium Alloys. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
Monotonic and cyclic torsion was used to investigate the effects of strain path on the development of the as-deformed and recrystallised microstructure and texture of two aluminum alloys (AA3103 and AA1050). Upon reversal of the torsional direction, the flow stress rapidly reached the same steady state level and grain structure, as those prior to strain reversal. However, monotonic and cyclic deformation to same net strain led to differences in texture and misorientation distribution.The recrystallised grain size after cyclic deformation was larger than that after monotonic deformation to the same net strain. This effect is due to a combination of a reduced driving pressure due to a lower fraction of high angle subgrain boundaries and a reduction of the density of favourable nucleation sites. The recrystallised material showed very weak textures, especially after cyclic torsion. After the largest monotonic strains AA1050 showed a retained B1 texture, while AA3103 started to display a weak Bs texture.
13.
Van Bakel, G. P. E. M. and D. N. Seidman (1995). "NEA method for rapid-determination of crystal orientation via Kikuchi patterns." Journal of Materials Research 10(12): 3026-3036.
14.
Van Boxel, S., M. Seefeldt, et al. (2005). "Visualization of grain subdivision by analysing the misorientations within a grain using electron backscatter diffraction." Journal of Microscopy 218(Pt. 2): 104-114.
The misorientation relative to the average orientation of a grain and the point-to-point relative misorientation along a line across a moderately cold deformed grain, calculated from an electron backscatter diffraction (EBSD) dataset, are analysed in detail by visualizing both the misorientation angle and the misorientation axis. The significance of monitoring the misorientation axis is illustrated by an example of a grain subdivided into a misorientation band structure. A new technique to visualize the subdivision structure by assigning colours to misorientations in such a way that the contrast is maximized within a grain is introduced and discussed. Furthermore, some methods for grain boundary reconstruction from EBSD datasets are compared with the map of the confidence index in order to provide a validation of the accuracy of these methods.
15.
van Daalen, M., R. Heilbronner, et al. (1999). "Orientation analysis of localized shear deformation in quartz fibres at the brittle-ductile transition." Tectonophysics 303(1-4): 83-107.
The crystallographic preferred orientation of fibrous quartz veins deformed under subgreenschist facies conditions along a temperature gradient from 270° to 370°C has been investigated. To explore the active mechanism during deformation of the quartz fibres, the complete crystallographic orientation of individual recrystallized grains and subgrains was determined by using a combination of CIP (computer-integrated polarization microscopy), EBSD (electron back-scatter diffraction), and additional specially developed image analysis techniques. It was found that the quartz fibres deformed along crystallographically controlled shear bands. From inverse pole figures of normals to the shear band boundaries it is evident that these bands occur along the positive and negative rhomb planes of quartz. It is suggested that they are initiated as fractures along these planes. Inside the shear bands, small grains broken off from the host grain show passive rotation of the lattice, consistent with the shear sense of the shear bands. Continued deformation and increasing temperature lead to different recrystallization microstructures inside and outside the shear bands and to a partial obliteration of the sharp orientation relationships.
16.
Van Driessche, I., G. Penneman, et al. (2003). Chemical approach to the deposition of textured CeO2 buffered layers based on sol gel dip coating. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.
The widespread use of vacuum techniques for the development of coated conductors, in which buffer and superconducting (REBa2Cu3O7δ) layers are deposited epitaxially on a substrate, is well established in the research environment. However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and film thickness and attaining independence of geometric constraints are areas in which many vacuum techniques will need sustained development in order to answer industrial demands. This work describes the deposition of CeO2 buffer layers based on sol gel dip coating under atmospheric environment and from aqueous precursor materials. Research has been performed towards the deposition of CeO2 buffer layers using the amorphous citrate method on sapphire substances and Ni-W foils. Coating is performed using the dip coating technique, which allows extension to a continuous system. The withdrawal speed and the thermal treatment have been optimized in order to obtain highly oriented (001) layers exhibiting a smooth and crack free morphology both on ceramic and metallic substrates. From the results it was concluded that sintering atmosphere and sintering temperature play a crucial role in the growth mechanism. This study describes the structural and morphological analysis of the thin layer with special attention to the difference between ceramic and metallic substrates.
17.
van Essen, C. G. (1970). 7th International Congress for Electron Microscopy, Grenoble.
18.
van Essen, C. G., E. M. Schulson, et al. (1970). Nature 225: 847.
19.
Van Geertruyden, W. H., H. M. Browne, et al. (2005). "Evolution of surface recrystallization during indirect extrusion of 6xxx aluminum alloys." Metallurgical and Materials Transactions A USA(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.
20.
Van Geertruyden, W. H., W. Z. Misiolek, et al. (2002). Formation of Recrystallization Textures after Hot Working of AA2014 and AA6063. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
This paper involves the investigation of the material response of two commercial aluminum alloys, 2014 and 6063, to thermo-mechanical processing parameters and the subsequent effects on the recrystallization behaviour. Samples of the 2014 and 6063 alloys were hot rolled at 350, 400, 480 and 500°C to reductions of 50% and 75%. The samples were subsequently solutionized at 500°C (2014) and 525°C (6063) for 1 hour. Light Optical Microscopy (LOM) was performed which showed increased recrystallization kinetics in the 6063 alloy relative to the 2014 alloy. The solutionized samples of the 2014 alloy showed a banded microstructure indicating recrystallization was inhibited in the normal direction. The microtexture of the samples was characterized using Electron Backscatter Diffraction (EBSD). Orientation Distribution Functions (ODF) and pole figures showed that the 6063 alloy displayed a copper rolling texture {112}<111> and an increasing cube recrystallization texture {001}<100> as the deformation temperature was increased. At low deformation temperatures, the 2014 alloy had a mixed Goss {110}<001> and Brass {011}<211> texture, while at higher temperatures and eductions, the Brass component was very strong. The 2014 recrystallized texture was predominantly a cube texture rotated 45 degrees about the normal direction.
21.
Van Geertruyden, W. H., W. Z. Misiolek, et al. (2005). "Surface grain structure development during indirect extrusion of 6xxx aluminum alloys." Journal of Materials Science 40(14): 3861-3863.
Two sets of direct chill cast Al-Mg-Si (6061) aluminum alloy billets were prepared: low Cr alloys (with Cr:Mn ratio of 1:1), and high Cr alloys (with Cr:Mn ratio of 2:1). Samples were indirectly extruded with starting billet temperature of 400 or 482 degrees C, ram speed of 1.3 or 2.6 mm/s, and extrusion ratio of 20 or 40. The effect of processing parameters on peripheral coarse grain (PCG) structure immediately after deformation in the small-scale indirect extrusion experiments was determined by light optical microscopy, electron backscatter diffraction and orientation imaging microscopy. In general, depth increased with increasing ram speed, Cr content, extrusion ratio and starting billet temperature. It is proposed that the PCG structure is a result of static recrystallization after deformation, and that the very small grain size existing at the surface of the extrudates were likely to have resulted from dynamic recrystallization and may contribute to an unstable structure.
22.
van Haaften, W. M., Y. Bi, et al. (2003). Recrystallization Nucleation during Annealing ofTi-Sulc Steel. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.
The nucleation mechanism of recrystallization of a cold rolled T-SULD steel was studied by Orientation Imaging Microscopy (OIM) in order to increase the fundamental understanding of the process and to generate a dataset for validation of a microstructural model. The annealing treatment was interrupted several times to capture different stages of the recrystallization process. In addition, using a hot stage SEM, in-situ observations were made of the recrystallization process. It appears that nucleation occurs by growth of subgrains or pre-existing nuclei, with little or no incubation (recovery) required. They have γ-fibre orientations and form at the grain boundaries and near internal shear bands of {111} grains. Due to the orientation gfradient present at these locations, the subgrains can form high angle grain boundaries (HAGBs), which allows them to grow quickly. The {001} grains recrystallize very late in the process due to a low stored energy. The preferred orientation of the recrystallized grains is thought to be related to the subgrain size distribution, where the particularly large subgrains are the ones that will grow.
23.
Van Houtte, P., S. Li, et al. (2005). "Deformation texture prediction: from the Taylor model to the advanced Lamel model." International Journal of Plasticity 21(3): 589-684.
The paper reports on a recent effort to develop a statistical (or Monte-Carlo) model for quantitative deformation texture prediction which is yet fast enough for implementation in every Gauss point of an FE simulation of a metal-forming process. The principles of Taylor-type models for the prediction of deformation textures of polycrystalline materials are reminded. This includes the full-constraints Taylor theory (every grain of a polycrystal undergoes the same plastic deformation), classical Relaxed Constraints Taylor theory (one or two of the components of the local velocity gradient tensor need not be the same for all grains) and multi-grain models (LAMEL model; mentioning of GIA model). The primal–dual structure of the equations relating strain rates with slip rates, and those relating stresses and resolved shear stresses on slip systems, is made clear. It is then possible to describe the basic philosophy and the mathematical implementation of a new model, called "advanced Lamel model" (ALAMEL). This model is more generally applicable than the previously developed LAMEL model, which is only valid for rolling. Both take interactions between neighbouring grains into account. Finally, quantitative comparisons are given between experimentally observed rolling textures and the predictions of the new model, as well as of other models: full-constraints and relaxed constraints Taylor, LAMEL, GIA, visco-plastic self-consistent and crystal plasticity finite element (CPFEM) models. This was done for IF steel (one thickness reduction) and for two aluminium alloys: AA1200 (five thickness reductions) and AA5182 (one thickness reduction). It was found that for AA1200, the new model is on average the best; for the two other cases, it is among the best models, but the LAMEL or CPFEM models are better. These results suggest that in spite of all simplifications, the ALAMEL model captures (and identifies) the domination mechanisms controlling the development of deformation textures in cubic metals.
24.
Van Swam, L. F. P., D. B. Knorr, et al. (1979). "Relationship between Contractile Strain Ration R and Texture in Zirconium Alloy Tubing." Metallurgical Transactions A 10(April): 483-487.
25.
Vanasupa, L., Y.-C. Joo, et al. (1999). "Texture analysis of damascene-fabricated Cu lines by x-ray diffraction and electron backscatter diffraction and its impact on electromigration performance." Journal of Applied Physics 85(5): 2583-2590.
The texture of electroplated Cu lines of 0.375, 0.5 and 1.5 µm widths with Ta and TiN barrier layers was analyzed using x-ray pole figure and electron backscatter diffraction (EBSD) techniques. Both techniques indicate a strong (111) fiber texture relative to the bottom surfaces of the trench for samples with a Ta barrier layer and a 400°C, 30 min, postelectroplating anneal. Samples with a TiN barrier and no anneal exhibit a weak (111) texture. For both barrier layers the quality of the texture, as measured by (111) peak intensity, fraction of randomly oriented grains and (111) peak width, degrades with decreasing linewidth. EBSD data also indicate (111) texture relative to the sidewalls of the trench in samples with a Ta barrier and postelectroplating anneal. Electromigration tests at 300°C of 0.36µm damascene Cu lines with the same process conditions show that samples with very weak (111) texture have median time to failures that exceed those of the strongly textured Cu lines. These results indicate that diffusion at interfaces, such as the Cu/barrier and Cu/overlayer interfaces, along with diffusion along an electroplating seam play more dominant roles in electromigration failure in damascene-fabricated lines than diffusion along grain boundaries within the interconnect.
26.
Vander Voort, G. F., E. P. Manilova, et al. (2004). A Study of Selective Etching of Carbides in Steel. Microscopy and Microanalysis 2004, Savannah, Georgia, USA, Cambridge University Press.
Etchants known to outline, color or attack various types of carbides in steels were developed in the 20th century. However, most studies of their selectivity and reproducibility were conducted prior to the development of modern electron analytical tools and techniques. Furthermore, confusion and contradictions over what these etchants reveal can be found in the literature. These etchants, if more carefully characterized, could be more useful as selective etchants for image analysis studies in quality control or research applications. A variety of steel compositions with anticipated carbide types have been characterized by EDS and EBSD and then subjected to these etchants to determine their usefulness.
27.
Vandermeer, R. A. and D. J. Jensen (1994). "Modeling microstructural evolution of multiple texture components during recrystallization." Acta Metallurgica et Materialia 42(7): 2427-2436.
A low cost, highly versatile electron backscattering diffraction system has been developed for an ElectroScan E3 environmental scanning electron microscope (ESEM). A P20 phosphor coated screen is placed in the microscope environment to image electron backscattering diffraction patterns (EBSP's). A CCD TV camera is used to view the patterns through a leaded glass port in the microscope specimen chamber. This system has a spatial resolution approaching 5 mu m and yields analyzable patterns at pressures of up to 6 Torr. With minor modifications this system may be adapted to fit any scanning electron microscope. Comparison of analyses of the grain boundary misorientation of a Ni-16Cr-9Fe alloy with this system and by selected area channeling patterns (SACP's), performed in a standard SEM, yielded excellent agreement between the two techniques. Owing to the capability to perform on-line analysis of EBSP's, the EBSP technique required only half the time as the SACP technique. The capabilities of the system are illustrated in a study of the grain boundary character distribution of Ni-16Cr-9Fe following thermomechanical treatment. (22 References).
28.
Vandermeer, R. A. and D. J. Jensen (1998). "The Migration of High Angle Grain Boundaries during Recrystallization." Interface Science 6: 95-104.
When plastically deformed metallic materials are annealed, new strain free grains emerge from the microstructure and grow by means of grain boundary migration until the deformation microstructure is eliminated. This process is called recrystallization. In this paper the various methods by which grain boundary migration rates are measured stereologically in order to characterize the growth process are described and compared using illustrations from recrystallization experiments on commercial AA1050 aluminum. It seems abundantly clear that during recrystallization of cold-deformed materials, isothermal grain boundary migration rates decrease with time and reasons for such a decrease are discussed. A new methodology whereby migration rates of the individual recrystallization texture components may be quantified by combining stereology and orientation imaging by the electron back scattered pattern analysis is outlined. By illustration, recent experiments on aluminum and copper are summarized documenting the slight growth rate advantage the cube texture component (001)[100] possesses during recrystallization of cold rolled material. The role of orientation pinning effects on grain boundary migration is described briefly. It appears that such pinning effects allow recrystallized grains emerging from the weaker deformation texture components to enjoy an average growth rate advantage over those emerging from the stronger deformation texture components.
29.
Vanderschueren, D., N. Yoshinaga, et al. (1996). Microtexture Analysis of Recrystallization of Ti-IF Steel. Eleventh International Conference on Textures of Materials, Xi'an, China, International Academic Publishers.
30.
Vanriet, C. and P. Demeester (1985). "Cavitation in a Dilute Superplastic Zn-O 5-Percent-Al alloy - A Cascade Mechanism for Cavity Generation." Scripta Metallurgica 19(7): 795-800.
31.
Varin, R. A., W. Lojkowski, et al. (1981). "Spreading of Extrinsic Grain-Boundary Dislocations on Grain-Boundaries Migrating in Thin Foil." Scripta Metallurgica 15(7): 795-798.
32.
Varnell, G. L., D. F. Spicer, et al. (1979). "High-speed, low-overhead electron beam direct slice writing system." Journal of Vacuum Science and Technology 16(6): 1787-93.
Electron beam writing systems have been primarily used for photomask and reticle fabrication because of the limited throughput achievable. A vector-scan beam writing system (EBSP) has been developed with a 1-1.25 mu m resolution capability and +or-0.25 mu m pattern overlay accuracy and a potential throughput capability of 14 3-in. slices/h for 1-1.25 mu m minimum pattern geometries and 20 3-in. slices/h for 2.5 mu m minimum pattern geometries. This paper discusses the throughput factors for vector-scan e-beam systems and describes the new developments and improvements to the major subsystems of the earlier photomask machine (EBM II) which were necessary to achieve this order of magnitude improvement in throughput. (15 References).
33.
Vatne, H. E. and E. Nes (1994). "The Origin of Recrystallization Texture and the Concept of Micro-Growth Selection." Scripta Metallurgica et Materialia 30(3): 309-312.
34.
Vatne, H. E., M. Karlsen, et al. (1996). Determination of Lattice Plane Spacings From Electron Back-Scatter Patterns. EUREM 11, Dublin, Ireland.
35.
Vatne, H. E., R. D. Doherty, et al. (1996). Deformation and Recrystallization of Hot Deformed Aluminum with High Initial Cube Texture. Eleventh International Conference on Textures of Materials, Xi'an, China, International Academic Publishers.
36.
Vatne, H. E., R. Shahani, et al. (1996). "Deformation of cube-oriented grains and formation of recrystallized cube grains in a hot deformed commercial AlMgMn Aluminum alloy." Acta Materialia 44(11): 4447-4462.
The cube orientation is usually found to be the strongest recrystallization texture component in annealed aluminium. The purpose of the present work was to obtain a better understanding of the cube orientation, both with respect to the behaviour of cube-oriented grains during deformation and the formation of recrystallized cube grains. Extensive use was made of the EBSP technique to characterize samples of a hot deformed AlMgMn alloy and plane strain compression tests were used to simulate hot rolling under a wide range of conditions of strain, strain rate and temperature. The investigations included: (i) the stability of cube-oriented grains during deformation, (ii) characterization of cube-oriented regions in the as-deformed state and (iii) nucleation of recrystallized cube grains. The work has demonstrated that cube-oriented grains present in the material prior to deformation remain orientation metastable during deformation and are deformed to bands. These cube bands have a unique subgrain size distribution with a long tail of large subgrains, making them very potent as nucleation sites for recrystallized grains. Nucleation of recrystallized cube grains takes place preferentially from those bands which are surrounded by the S deformation texture component.
37.
Vatne, H. E., S. R. Hognes, et al. (1996). Texture Evolution during Wire Drawing and Its Influence on Subsequent Cutting Operations in Steel Wool Production. Eleventh International Conference on Textures of Materials, Xi'an, China, International Academic Publishers.
38.
Vaudin, M. D. and J. P. Cline (1994). Texture measurements in Al2O3 using BEKP. Fifty-Second Annual Meeting Microscopy Society of America/Twenty-Ninth Annual Meeting Microbeam Analysis Society, New Orleans, LA, San Fancisco Press, Inc.
39.
Vaudin, M. D. and W. C. Carter (1991). "Studies of Ceramics using Backscatter diffraction Patterns in the Scanning Electron Microscope."
40.
Vedula, V. R., S. J. Glass, et al. (1999). Predicting microstructural-level residual stresses and crack paths in ceramics. ICOTOM 12: 12th International Conference on Textures of Materials, Montreal, National Research Council of Canada, Building M-55, Ottawa, ON K1A 0R6, Canada.
Microstructural-level residual stresses arise in ceramics due to thermal expansion anisotropy. These stresses are high enough to cause spontaneous microcracking during the processing of these materials. The orientation data obtained by backscattered electron diffraction and grain boundary energies obtained by AFM were used in conjunction with an object oriented finite element analysis package (OOF) to predict the magnitude of residual stresses in alumina. Crack initiation and propagation were also simulated based on the Griffith fracture criterion.
41.
Vehoff, H., A. Nykyforchyn, et al. (2004). "Fatigue crack nucleation at interfaces." Materials Science and Engineering A 387-389: 546-551.
Fatigue crack nucleation at grain boundaries near the endurance limit was examined combining the results of fatigue tests with local orientation measurements and with finite element calculations. Coarse-grained thin sheets were examined in which the orientation and inclination of each boundary could be measured directly. These results were used as input for FEM calculation in which the stress concentrations near the grain boundaries were calculated. In the fatigue tests, the boundaries, at which the first cracks nucleate, were measured by a replica technique. A comparison between the experimental results and the FE calculation showed that the cracks nucleated and propagated along the boundaries with the largest stress concentration. When a crack hits a boundary with a lower stress concentration, it either stops or propagates transgranularly depending on the local stress concentration given by the microstructure. From these results, it can be concluded that elastic strain incompatibility combined with the microstructure (grain size and orientation) can be used to predict the crack nucleation sites and the scatter in life time for fatigue near the endurance limit.
42.
Venables, J. A. and C. J. Harland (1973). Electron back-scattering patterns-a new crystallographic technique for use in the S.E.M. Conference on Scanning Electron Microscopy: Systems and Applications, London, UK, Inst. Phys.
The technique consists of observing the angular distribution of back-scattered electrons on a screen in the S.E.M. specimen chamber; the patterns so obtained contain crystallographic features termed high angle Kikuchi patterns. Because these patterns arise from the back-scattered electrons they have been called electron back-scattering patterns (E.B.S.P.). E.B.S.P.'s have the following features: they are extremely simple to obtain; very wide angle patterns can be obtained so that there is no possibility of mistaking the orientation; the size of the region from which the information comes is limited by the cascade size in the material; and large beam currents can be put into this spot. (3 References).
43.
Venables, J. A. and C. J. Harland (1973). "Electron back-scattering patterns-A new technique for obtaining crystallographic information in the scanning electron microscope." Philosophical Magazine 27(5): 1193-200.
It is shown that the angular distribution of back-scattered electrons can be observed in a scanning electron microscope, and that the patterns observed can be used to obtain crystallographic information about the specimen. The patterns are termed electron back-scattering patterns (E.B.S.P.). The use of these patterns as a crystallographic technique is shown to have several significant advantages over two other techniques currently in use in scanning electron microscopes. (11 References).
44.
Venables, J. A. and R. Bin-Jaya (1977). "Accurate microcrystallography using electron back-scattering patterns." Philosophical Magazine 35(5): 1317.
45.
Venables, J. A., C. J. Harland, et al. Accurate Microcrystallography in the S.E.M. Thirty-Eighth Annual EMSA Meeting.
46.
Venables, J. A., C. J. Harland, et al. (1994). Electron diffraction in UHV SEM, REM, and TEM. Fifty-Second Annual Meeting Microscopy Society of America/Twenty-Ninth Annual Meeting Microbeam Analysis Society, New Orleans, LA, San Fancisco Press, Inc.
47.
Venables, J. A., P. S. Flora, et al. (1990). "New Developments in Electron-Spectroscopy and Imaging." Institute of Physics Conference Series 98(289-294).
48.
Venegas, V., F. Caleyo, et al. (2005). "EBSD study of hydrogen-induced cracking in API-5 L-X46 pipeline steel." Scripta Materialia 52(2): 147-152.
The spatial distribution of plastic deformation and grain orientation surrounding hydrogen-induced cracks (HIC) is investigated in samples of API-5L-X46 pipeline steel using scanning electron microscopy and electron backscattering diffraction (EBSD). This work shows direct experimental evidence of the influence of microstructure, microtexture and mesotexture on HIC crack path.
49.
Verbeken, K. and L. Kestens (2002). Local Strain Heterogeneities after Cold Rolling of an Ultra Low Carbon Steel. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
The orientation gradient within grains of different texture fibres was studied for an ultra low carbon steel after a cold rolling reduction of 60%. The substructure was investigated by detailed OIM scans. The formation of strain heterogeneities within the elongated grains was revealed and a fragmentation of these grains was found. The strain heterogeneities were investigated for two different families of grains: {110}/RD and {111}/ND fibre orientations. For a number of orientations along these fibres, the misorientation profiles within these grains were calculated. It was found that ND- and RD-fibre grains exhibit an entirely different fragmentation behaviour which profoundly affects the nucleation processes in these orientations.
50.
Verbeken, K. and L. Kestens (2004). Oriented Nucleation and Selective Growth during Secondary Recrystallization in Ultra Low Carbon Steels. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
After primary recrystallization, on further annealing, abnormal grain growth occurred in ultra low carbon steel. Texture evolution was studied by comparing the orientations after complete secondary recrystallization, with on one hand the nuclei for abnormal grain growth and on the other hand the selective growth products of the primary recrystallized matrix. The influence of both mechanisms could be identified in the final texture.
51.
Verbeken, K. and L. Kestens (2005). Nucleation of Secondary Recrystallization in Ultra Low Carbon Steel. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
The nucleation stage of secondary recrystallization has never been considered in detail. During the present study, nucleation of abnormal grain growth in ULC steel was studied. A specific nucleation mechanism was identified. This mechanism involved the disappearance of low angle grain boundaries, which gave rise to the onset of a local grain coalescence mechanism that clusters grains that were only separated by low angle grain boundaries. The impact of the nucleation stage remained visible in the texture that was obtained after complete abnormal grain growth.
52.
Verbeken, K., L. Kestens, et al. (2003). "Microtextural study of orientation change during nucleation and growth in a cold rolled ULC steel." Scripta Materialia 48: 1457-1462.
Texture development during the recrystallization of an ultra low carbon steel is shown to be largely dependent on the rolling reduction. Comparison of the recrystallization process for two different rolling reductions indicates that in each case a different recrystallization mechanism is responsible for the principal features of the annealing texture.
53.
Verbeken, K., L. Kestens, et al. (2004). Evaluation of Selective Growth in a Fe-2.8%Si Single Crystal Using Rodrigues-Frank Space. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
A Fe-2.8%Si single crystal was scratched in order to randomise the texture in the neighbourhood of the notch. Annealing resulted in recrystallization and grain growth starting from the deformed zone. Misorientations between the single crystal matrix and the grown grains were gathered and were studied in order to investigate the possibility for selective growth based on a specific misorientation. However, instead of studying the misorientation angle or axis profiles separately in a 1D or 2D projection, a full misorientation analysis was carried out in the 3-dimensional Rodrigues-Frank misorientation space, which offers an unambiguous interpretation of the data because no features are hidden or masked by a projection. It is concluded that the selective growth phenomenon following the <110>26.5deg misorientation relationship is strongly supported by the gathered orientation data, after appropriately normalizing these data with respect to a random misorientation distribution.
54.
Verbeken, K., L. Kestens, et al. (2005). "Re-evaluation of the Ibe-Lucke growth selection experiment in a Fe-Si single crystal." Acta Materialia 53(9): 2675-2682.
Selective growth effects during primary recrystallization have been widely discussed but so far no convincing proof has been provided. In the search for a more fundamental understanding of texture formation during the growth stage of static recrystallization, the historic growth experiment by Ibe and Lticke was re-evaluated by making use of modern electron backscattering diffraction equipment. Moreover, the non-random character of the nucleation texture was considered and the misorientations between the recrystallised grains and the single crystal matrix were examined in the 3D Rodrigues-Frank misorientation space. It was seen that the volume fraction of misorientations around the exact < 110 > 26.5 deg misorientation increased by a factor of 10 during growth. This is believed to provide unambiguous evidence for the occurrence of selective growth during the recrystallization process under consideration.
55.
Verbeken, K., M. D. Nave, et al. (2003). Selective growth in a scratched Fe-2.8%Si single crystal. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.
Scratching and annealing of a Fe-2.8%Si single crystal resulted in recrystallization and grain growth in the neighborhood of the notch. Misorientations between the grown grains and the single crystal matrix were measured, and a frequency distribution of misorientation angles was used to investigate the possibility of selective growth based on misorientation. The misorientation angles used in the present analysis were those having an axis [uvw] nearest to one of the <110> variants. In order to take into consideration the texture before growth, the texture of the deformation-affected zone near the scratch was measured. The misorientation profiles before and after growth were compared. It is concluded that the well-known selective growth phenomenon following the <110>26.5deg misorientation relationship is supported by the orientation data.
56.
Verlinden, B., P. Bocher, et al. (2000). "Orientation Imaging Microscopy Investigation of Bainite-Austenite Structures using a Field Emission Gun Microscope."
57.
Verlinden, B., P. Bocher, et al. (2001). "Austenite texture and bainite/austenite orientation relationships in TRIP steel." Scripta Materialia 45: 909-916.
A bainitic medium carbon steel with 10-15vol.% of retained austenite has been used to measure the texture of recrystallized and deformed austenite and of the corresponding bainite. The local orientations of bainite and retained austenite, and their orientation relationships, hve been measured with an automated EBSD devie mounted on a FEGSEM.
58.
Vernon-Parry, K. D., I. Brough, et al. (1999). "A Novel Method for Studying the Regrowth of Implanted Silicon." Institute of Physics Conference Series(164): 473-476.
59.
Vernon-Parry, K. D., S. Galloway, et al. (2003). Correlation between G-line luminescence and structure of boundaries in electron-irradiated EFG silicon. Microscopy of Semiconducting Materials Conference, Cambridge, UK, Institute of Physics, Bristol, UK.
Edge-defined film-fed growth (EFG) is an economical method of producing multi-crystalline silicon ribbon for solar cells. Such silicon is heavily doped with carbon. Scanning cathodoluminescence studies of electron-irradiated EFG silicon show that the dominant line in the luminescence spectrum is the G-line (due to CsCi defects). The optical behaviour of the grain boundaries in this material is found to depend on the boundary structure, which is determined by electron backscattered diffraction analysis. A possible explanation for the variation in optical behaviour is suggested.
60.
Vernooij, M. G. C. (2005). Dynamic recrystallisation and microfabric development in single crystals of quartz during experimental deformation, Eidgenoessische Technische Hochschule Zuerich (Switzerland). Ph.D.: 140.
To investigate the effect of dynamic recrystallisation on CPO development, natural quartz single crystals were experimentally deformed under conditions where dynamic recrystallisation and CPO development are known to occur (temperature 800°C, confining pressure ∼1.2 GPa, strain rate 10-6-10-7 s-1, bulk finite strain 5-50%, 1 vol% added water). Samples were uniaxially deformed in different crystallographic starting orientations. The highly heterogeneous microstructures and textures of the deformed samples were analysed by light microscopy, electron backscatter diffraction (EBSD) analysis, transmission electron microscopy (TEM), secondary electron imaging and cathodoluminescence. It could be shown that the experimentally produced microstructures and CPOs, reported in this thesis, result from three different reorientation processes: (1) Crystal reorientation by glide controlled lattice rotation, (2) crystal reorientation by precipitation and growth of new grains and (3) crystal reorientation by rotation of fracture fragments. In the literature it is generally assumed that dynamic recrystallisation takes place as a consequence of dislocation creep. New grains are considered to develop by progressive subgrain rotation and further evolve by grain boundary migration. The experiments show, however, that new recrystallised grains can also be created by precipitation from solution as well as by rotation of fracture fragments along crystallographically oriented microfactures. The recrystallised grains do not inherit the CPO from their host grains, but assume orientations most suitable for glide during progressive grain boundary migration.
61.
Vevecka, A. and T. G. Langdon (1994). "An Investigation of Grain Rotation and Grain Elongation in a Superplastic Alloy." Materials Science and Engineering A 187(2): 161-165.
62.
Viana, C. S. D. C., A. Dos Santos Paula, et al. (2004). Evolution of the recrystallization texture in an IF steel. Advanced Materials Forum II: proceedings of the II International Materials Symposium: Materials 2003 and XI Encontro Sociedade Portugesa de Materials, 2003 ATERIAIS, Caparica, Portugal.
Cold rolling experiments were carried out on an IF steel. The samples were partially and totally recrystallized in a muffle type vertical furnace at 650 degrees C for 30 and 45 seconds, 1, 2, 3 and 5 minutes in order to study the formation of the new recrystallization nuclei and their orientation relationships with the surrounding deformed matrix. Both microstructure and texture were examined by SEM. The texture was analyzed by Electron Back Scatter Diffraction (EBSD) and Orientation Image Microscopy (OIM), and represented via the ODF method. The ODF for each sample was the input in a computer calculation specifically created to show the evolution of the principal orientations during annealing. The calculation showed that the first orientation that was formed was (110) 1 1-0, in agreement with the results obtained by others. This work aims at providing another tool to study recrystallization texture by using a computer program specifically created to show the evolution of the principal orientations during the annealing through the subtraction of the spherical harmonic series.
63.
Viana, C. S. D. C., A. L. Pinto, et al. (2006). "Analysis of ridging in three ferritic stainless steel sheets." Materials Science and Technology 22(3): 293-300.
In the present work, three types of ferritic stainless steel sheets AISI 430A (16%Cr), AISI 430E (16%Cr, 0.36%Nb) and AISI 434 (16%Cr, 1%Mo), known to display different ridging behaviours, were characterised in both microstructure and texture using optical metallography and electron backscatter diffraction techniques. It was concluded that surface microridging is a result of the differential plastic behaviour of {111}<uvw> and {001}<uvw> grain colonies existing in the sheet; severe ridging (undulations) is a consequence of through thickness texture and microstructure inhomogeneities that lead to grain buckling under internal compressive stresses.
64.
Viana, C. S. d. C., F. S. Candido, et al. (2005). An EBSD Analysis of the Origins of Ridging In AISI 430 Steel Sheets. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
In the present work the characterisation of both the microstructure and the microtexture of two ferritic stainless steel sheets - AISI 430 (Fe17% Cr) and AISI 434 (17% Cr, 1% Mo) - known to display different ridging behaviours, was carried out by optical metallography, EBSD and OIM techniques. It was concluded that severe ridging is a consequence of: (a) presence of {111}<uvw> and {001}<uvw> colonies of grains alternating throughout the sheet plane; (b) through thickness texture inhomogeneity with layers of {001}<110> oriented large grains of low Rvalues sandwiched between layers of higher R-value textured material.
65.
Viana, C. S. D. C., J. C. Paredes, et al. (1999). EBSD analysis of shear banding in α-Brass. Twelfth International Conference on Textures of Materials (ICOTOM 12), McGill University, Montreal, Canada, NRC Research Press.
66.
Villechaise, P., L. Sabatier, et al. (2002). "On slip band features and crack initiation in fatigued 316L austenitic stainless steel: Part 1: Analysis by electron back-scattered diffraction and atomic force microscopy." Materials Science and Engineering A 323(1-2): 377-385.
Electron back-scattered diffraction (EBSD) and atomic force microscopy (AFM) have been used to study surface slip features on 316L austenitic stainless steel polycrystals tested in the low cycle fatigue range. EBSD investigations allow activated slip planes to be identified for each grain and the local inclination of these slip planes to the surface to be calculated. AFM allows the height of steps induced at the surface along slip bands to be measured and the local morphology of extrusions to be characterized at a nanometer scale. In this study, both techniques are used on the same surface in order to combine crystallographic and topographic information. Based on the results, a schematic model of the slip band emergence is proposed.
67.
Viswanathan, G. B., E. Lee, et al. (2005). "Direct observations of dislocation substructures formed by nano-indentation of the a phase in an a/b titanium alloy." Materials Science and Engineering A 400-401: 463-466.
Nano-indentation has been used to assess the hardness of equiaxed grains of α-Ti as a function of orientation. Surface normals of these grains in metallographic sections were assessed using orientation imaging microscopy. Thin membranes of material from below a series of nano-indentations were excised by use of a dual-beam focused ion beam instrument. In this way, the dislocation substructures beneath individual indentations were characterized using transmission electron microscopy, permitting an identification of both statistically stored and geometrically necessary dislocations. Material: Ti-6Al-4V.
68.
Vogel, S., P. Klimanek, et al. (1996). "Effect of texture on the development of grain size distribution during normal grain growth." Scripta Materialia 34(8): 1225-1230.
Isothermal grain growth of brass and copper are analyzed by optical microscopy, neutron diffraction and EBSP-measurement (Electron Backscattering Pattern). The EBSP-technique is to used to separate the average grain sizes and the grain size distributions of the main texture components in both materials. It is found that the average grain size of grains of different orientations in the investigated materials are statistically different, and the results are discussed with reference to the statistical models presented. [References: 17]
69.
Vollbrecht, A., M. Stipp, et al. (1999). "Crystallographic orientation of microcracks in quartz and inferred deformation processes: a study on gneisses from the German Continental Deep Drilling Project (KTB)." Tectonophysics 303(1-4): 279-297.
This study was carried out on four gneiss samples from the German Continental Deep Drilling Project (KTB) taken at depths between 556 and 8633 m. The crystallographic orientation of microcracks in quartz was determined by a combination of the electron channelling pattern method (ECP) and U-stage microscopy. The distinct preferred crystallographic orientations of various crack generations point to different processes of crack initiation and propagation which partly seem to be depth-dependent. For older healed cracks, a crystalplastic initiation due to dislocation pile-up and related lattice distortion is indicated by cracking normal to prominent slip directions, which are <α > at lower or [c] at comparatively higher temperatures. In contrast, younger open cracks preferentially formed on crystallographic planes with low surface energy (rhombs and prisms), which is interpreted in terms of pure elastic crack mechanisms. Because of the thermoelastic anisotropy of quartz, internal stresses resulting from thermal contraction during cooling may be the main driving force for the initiation or further propagation of cracks parallel to the c-axis. Crack propagation preferentially affects grains with crystal lattices and operating crack mechanisms being in a direction appropriate to the applied external (tectonic) stresses. This selective cracking explains why cracks also show constant orientations with respect to geographic directions up to regional dimensions.
70.
Volovitch, P., V. Traskine, et al. (2002). "Grain boundary wetting statistic in Zn/Ga system and its application to grain boundary energy spectrum estimation." Interface Science 10(4): 303-309.
The grain boundary statistic in zinc polycrystals in contact with saturated Ga(Zn) melt has been studied. The misorientation angle distributions for zinc thin foil and zinc plates were obtained. The influence of the misorientation angle theta value on the wetting probability p of grain boundaries was observed. The grain boundary energy distribution parameters were obtained by using the p(theta) relationship. The dihedral angles in triple lines of non-wetted zinc samples were also measured and their distribution was used to obtain the grain boundary energy distribution function. The parameters obtained by two different methods correspond to one other.
71.
Voort, G. F. V. and E. P. Manilova (2005). "Hints for imaging phases in steels." Advanced Materials & Processes 163(2): 32-37.
The microstructure of metals and alloys can be quite complex, particularly alloy systems such as iron-based alloys. A good understanding of physical metallurgy, the role of composition and processing on structure formation and modification, and idea of the approximate expected hardness of different phases or constituents may help narrow the range of possible phases that might be present. This paper discusses methods learned from experience, and presents a number of hints and tricks to make the metallographer's job easier and more precise. It covers ways to improve the visibility and hence the identification of so-called "white-etching phases" in steels (ferrite and delta ferrite, cementite and retained austenite) etched with standard reagents where the matrix can vary considerably. Various high-tech tools for phase identification such as X-ray diffraction, transmission electron microscopy, energy-dispersive spectroscopy, electron-energy loss spectroscopy, and electron-backscattered diffraction are also presented.
72.
Vorhauer, A., T. Hebesberger, et al. (2003). "Disorientations as a function of distance: a new procedure to analyze local orientation data." Acta Materialia 51(3): 677-686.
A new procedure for analyzing local orientation data has been developed to investigate the relationship between orientations and data point distances. The key idea is to determine the distribution of the disorientation angle as a function of the distance between the data points. The evolution of the disorientation angle distribution with increasing data point distance provides quantitative information about average local variation of thecrystal orientation which can be used to classify structural elements, to determine the average structural size, and allows the quantification (crystallographically) of the boundaries between adjacent structural elements.The potential of this analyzing procedure is demonstrated by investigating the orientation data of Electron Backscattering Diffraction (EBSD)-measurements performed on severe deformed copper samples. The benefits in comparison to other commonly used methods to quantify local disorientations are discussed.
73.
Vreeling, J. A., V. Ocelík, et al. (2002). "Ti–6Al–4V strengthened by laser melt injection of WCp particles." Acta Materialia 50: 4913-4924.
The laser melt injection (LMI) process has been explored to create a metal–matrix composite consisting of 80 μm sized WC particles embedded in a Ti–6Al–4V alloy. In particular the influences of the processing parameters, e.g. power density, scanning speed and powder flow rate, on the dimensions and microstructure of the laser track have been examined. The microstructure was investigated by advanced transmission electron microscopy including energy filtering techniques and scanning electron microscopy with an integrated electron back-scatter diffraction/orientation imaging microscopy. Typical dimensions of a single laser track are a width of 1.8 mm and a depth of 0.7 mm. The volume fraction of the WC particles is about 0.25–0.30. An important finding is that the particle distribution is homogeneous and that the particles are injected over the whole depth and whole width of the melt pool. Only occasionally a crystal orientation relation between WC, W2C and TiC is observed. A substantial increase in wear resistance was observed, i.e. 0.5 × 10-6mm3 /Nm for the WCp laser embedded and 269 × 10-6mm3 /Nm for the untreated Ti–6Al–4V alloy at the same contact stress (20 MPa).
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