Materials Science Forum Vols. 702-703

Abstract: Electro-deposited pure iron has a quite sharp and isotropic <111>//ND fiber texture and a needle-shaped grain elongated in ND. This pure iron shows an r-value exceeding 7, which is difficult to explain from the texture alone. In this study the deformation behavior of electro-deposited pure iron was investigated to reveal the mechanism behind the extremely high r-value. The post-deformation surface slip lines indicated that the particular <110> plane slips, which are perpendicular to ND, exclusively act in the specimen. The tensile deformation caused by this slip system does not require any decrease in thickness, hence the extraordinary high r-value is mainly attributable to this limitation of the active slip system. Presumably, the needle-shaped microstructure affected the limitation of the slip system.

Abstract: Present work describes the evolution of microstructure and texture in W-26Ni-26Fe-13Co and W-28Ni-12Fe-10Co alloys during cold rolling. These alloys consist of two phases i.e. W-base (bcc) and matrix (fcc) in sintered and cold rolled conditions. Microchemistry obtained by electron Probe Micro Analyser (EPMA) clearly indicates that the extent of alloying is very less in W phase. The matrix phase mainly consists of Ni, Fe Co and W. The development of texture in both the W and matrix during cold rolling has been described in terms of α, γ and β fibres for bcc and fcc phases, respectively.

Abstract: The present work describes the influence of texture and mechanical properties anisotropy on ballistic performance of an Aluminium-6063 extruded rod. It has been observed that the centre region of the extruded rod exhibits better strength, elongation and charpy impact values than the peripheral region. Texture of the extruded rod is measured from centre towards the periphery. A significantly variation in texture has been observed from the centre towards the periphery. Ballistic experiments are conducted on 80 mm thickness extruded samples by impacting them with 7.62 mm armour piercing projectile at 0° angle of impact at 840±15 m/s velocity. Results show that the centre of the extruded rod displays much improved ballistic performance than the periphery, which has been attributed to the strong {111} fibre texture present at the centre.

Abstract: Mechanical property anisotropy in terms of in-plane anisotropy (A_IP) of yield strength, and work hardening behavior of a heat treated 7010 aluminum alloy sheet has been investigated. The specimens were given two different types of heat treatments that result in a unique single rotated Brass-{110}á556ñ component with different texture intensity and volume fraction of recrystallization. It has been observed that the A_IP increases with increase in texture intensity and volume fraction of recrystallization. The results are discussed on the basis of Schmid factor analyses in conjunction with microstructural features namely, grain morphology and precipitation. On the other hand, work hardening behavior appears to be significantly affected by the microstructural features rather than type of texture present in the samples.

Abstract: Two grades of Steel, with tempered martensitic structure, were used for fatigue tests. From such tests, samples were obtained with significant differences in the probability of fatigue failure. The latter was related to surface/sub-surface misorientation developments and developments in compressive residual stresses. A combination of glancing incidence X-ray diffraction (GIXRD) and high resolution cross-sectional EBSD (electron back scattered diffraction) were used. The study brings out a clear correlation between misorientation, residual stress and fatigue life.

Abstract: The present study deals with nanoindentation behavior of commercial Zircaloy 2 and high purity (5N purity) crystal bar Zirconium. The effect of crystal orientation was studied through high resolution electron diffraction, while a finite element model was developed to extract yield strength and strain hardening exponent from nanoindentation data. The study brings in clear signatures of orientation dependence of mechanical properties in hexagonal Zirconium.

Abstract: The aerospace industry uses a variety of materials in different forms like sheets, forgings, extruded rods, welded components and machined components for launch vehicle and satellite applications. As lighter and stronger materials are the aims of the aerospace industry, aluminium alloys are the most widely used materials in the in the aircraft and aerospace industries. These aluminum alloys used in the aerospace industry are subjected to a variety of processing operations, either in the sheet form after rolling, forging, heat treatment and machining conditions, to realize the final product implies that these alloys exhibit a wide range of properties depending on the processing conditions. Texture formation in a material takes place during its various processing stages. The actual orientation distribution in a poly crystal is the result of the manufacturing processes applied. In this context, it is important to characterize the evolution of texture, both macro and micro texture, in AA7075 and AFNOR7020 alloys, which are two of the important high strength aluminum alloys used in the Aerospace industry. This paper deals with the results of the crystallographic texture measurements carried out on the cold rolled and artificially aged AA7075 and AFNOR7020 aluminium alloys. Results obtained from the pole figure analysis, Orientation Distribution Function (ODF) method and estimation of the various fibres present in the cold rolled material and the volume fraction of the texture components are discussed in detail for the alloy. Results of the micro texture measurements using the EBSD are presented, explained and analyzed in detail. A comparison of the inverse pole figures (IPFs), Image Quality (IQ) maps, Misorientation angle, Grain Orientation Spread (GOS), Kernal Average Misorientation (KAM), CSL boundaries, Grain size and Grain boundary character distribution (GBCD) for materials cold rolled to different reduction for the alloy are done and analyzed. Conclusions are drawn regarding the evolution of texture from the above analysis. Deformation texture components Cu, Bs and S increase from the starting material as the rolling percentage increases. On the other hand, recrystallization texture components of Goss and Cube are observed to be weak. AFNOR7020 Alloy developed a stronger texture compared to the AA7075 alloy. S component of texture is stronger in AA7075 alloy whereas the Bs component is stronger in AFNOR7020 alloy. This is attributed to the shear banding which was found absent in the other alloy.

Abstract: In present study microstructural evolution during swaging on aluminium alloy based metal matrix composite (MMC) reinforced with 15% volume fraction silicon carbide (SiC) particles is presented. Samples were swaged at room temperature in steps with reducing die dimensions using rotary swaging technique. SEM and TEM are used to study the microstructural characteristics of swaged samples. SEM observations were made to understand the flow and deformation characteristics of deforming aluminium matrix in the presence of second phase and reinforced SiC particles during swaging. TEM observations on swaged samples confirmed the formation of ultra-fine grains in Al-15%SiC MMC. It is shown that the dynamic recrystallisation occurring in the proximities of second phase particles during the deformation at room temperature, leads to very fine grained microstructure.

Abstract: This paper describes nucleation and grain coarsening at very early stages of recrystallization in AA3104 aluminum alloy containing complex structure of second phase particles. Measurements of individual sub-cell orientations in ECAP-processed and slightly annealed structures were possible by using TEM-based orientation mapping in combination with recrystallization carried out in the microscope. The results were compared with those obtained by SEM/EBSD system. The investigation shows that the 40^o<111>-type relation occurs rarely, and the rotation axes of misorientations between deformed and recrystallized areas were strongly scattered. Grouping of the misorientation axes near the <012>, <221>, <112> and <110> crystallographic directions was noticeable.

Abstract: The present work describes the study of mechanical properties anisotropy of two binary alloys namely, Ti-8Nb and Ti-12Nb in hot rolled condition. These alloys were unidirectionally hot rolled to 80 % reduction at 800 °C and subsequently air cooled. The alloys Ti-8Nb and Ti-12Nb consist of mainly α and α″ phases, respectively and small volume fractions of β phase in hot rolled condition. Both the alloys exhibit non-basal main texture components. The ODF plots display weak, continuous and inhomogeneous [0001]||ND and [001]||ND fibres for the alloys Ti-8Nb and Ti-12Nb, respectively. In plane anisotropy (A_IP) and anisotropy index (δ) were calculated from tensile results. Finally, an attempt has been made to correlate in plane anisotropy and yield locus to that of texture present in the hot rolled materials.