Papers by Author: A.K. Singh

Abstract: The development of preferred grain orientation has been investigated in the directionally solidified samples of Tb_0.3Dy_0.7Fe_1.95 as a function of pulling speed viz. 10, 40, 70 and 100 cm/h. The study indicates that at lower solidification rate (10 cm/h) growth of and texture components are preferred, whereas, texture component becomes dominant at higher pulling rate (100 cm/h). However, as the solidification progresses, growth of texture component is observed subduing the other components. Consequently, the magnetostriction improves from 1100 to 1350 micro-strains with higher pulling speed.

Abstract: This paper reports the effect of Ho on the microstructure, texture and magnetostrictive properties of Tb_0.3Dy_0.7-xHo_xFe_1.95 (with x = 0, 0.05, 0.1, 0.15 and 0.2) alloys. The alloys were vacuum induction melted and directionally solidified by modified Bridgman technique. Ho addition has been found to improve the magnetostriction at lower concentration due to absence of deleterious pro-peritectic (Tb,Dy)Fe3 phase. The static strain co-efficient is found to be better in Ho added alloys and the prevalence of strong and texture is attributed to be the reason.

Abstract: This study describes the influence of texture and associated mechanical properties on ballistic performance of Aluminium-7017 alloy in two different (unidirectional and clock) hot rolling conditions. The change in texture has been explained in terms of β fiber in hot rolled and T6 tempered condition. A marginal variation in strength and hardness is observed with changing the mode of rolling, whereas Charpy impact values are found to be varying considerably. Results show that the unidirectional rolled material exhibits improved ballistic performance than that of the clock rolled plate. This has been attributed to different textures present in both the plates.

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: 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: Present work describes the evolution of texture during different modes of deformation by cold rolling of a Gum metal or multifunctional β titanium alloy. The starting and cold rolled materials exhibit the presence of β and β with small amount of stress induced martensitic (α˝) phases, respectively. The development of texture has been explained in terms of α and γ fibres. The bulk hardness appears to be independent of modes of deformation by cold rolling. The yield surfaces of as received and solution treated samples exhibit marked anisotropy which persists during different modes of deformation by rolling.

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.

Abstract: This work describes the development of texture during hot rolling of two alloys namely, Ti-12Nb and Ti-16Nb. The alloys have been unidirectionally hot rolled to 80 % reductions at 800°C and air cooled. Both the alloys show the presence of a² (orthorhombic) and small volume fraction of b (bcc) phases in hot rolled condition. The alloy Ti-12Nb exhibit moderate intensity texture while the alloy Ti-16Nb displays quite strong texture. The high overall intensity of texture in alloy Ti-16Nb in 80 % HR specimen can be attributed to the presence of large volume fraction of b phase in comparison to that of the alloy Ti-12Nb. This has been extended to study the textural changes after b solution treatment. This heat treatment consists of two types of phase transformations that are a² ® b ® a² and a² ® b ® a after water quenching and furnace cooling from β phase field.