Satyaveer Singh Dhinwal

The texture evolution is wearing the signature of the deformation path in plastic deformation. In asymmetric rolling, plain strain compression and shear are the main components of the imposed strain. In this work, viscoplastic self-consistent (VPSC) simulations of the texture evolution were used to determine the combination and sequence of the two deformation components. It has been found that the deformation path is composed of two parts in asymmetric rolling: it is first essentially rolling, followed by the simple shear process. Simultaneous rolling and shear process cannot produce the observed textures, while the decomposed simulation can reproduce it faithfully.

Systematic single pass rolling experiments were carried out at room temperature on extra low carbon steel by varying the roll diameter ratio between 1:1 to 1:2 and thickness reduction per pass in the range of 20–75%. The aim of this study was to define the conditions under which the rolling texture can transit into a shear texture. The consequences for grain fragmentation, tensile strength, recrystallization texture, and grain growth kinetics were also studied. It was found that in a certain range of thickness reduction per pass and asymmetric ratio, an effective rotation towards the shear texture takes place in conventional rolling. The value of the shear coefficient factor (shear strain rate/rolling strain rate) in asymmetric rolling depends on the selection of thickness reduction per pass. The measured value of shear coefficient was found to be independent of the number of passes used in asymmetric rolling. The consequence of arising shear textures is an acceleration of grain fragmentation. After rapid heat treatment, both tensile strength and recrystallization kinetics of asymmetric rolled sheets showed merits over the conventional rolling. Only the evolved Goss orientation from asymmetric conditions of deformation shows higher stability than any other preferred shear texture components after complete recrystallization.

Multi-pass rolling was carried out on extra-low carbon steel at room temperature by imposing different ratios of asymmetry in the roll-diameters as well as by conventional mode. The aim of this study is to understand the effect of shear deformation due to the asymmetric conditions on the development of the rolling texture and the possibilities of propagating the shear deformation into the mid-thickness area of the sheet. The trends of the measured texture developments in both symmetric and asymmetric rolling indicate their dependence primarily on the stability and fraction of the Goss {110} and the rotated cube {001} orientations. The effects of asymmetry conditions were further examined on the microstructure evolution and were correlated to the increased orientation inhomogeneity and grain fragmentation. Both texture and microstructure development showed their dependence on the applied thickness reduction per pass, on the total thickness reduction of the sheet as well as on the degree of the imposed asymmetry. It was found that shear textures can be obtained by asymmetric rolling at conditions where all three parameters—asymmetry ratio, strain in one pass, and the total accumulated strain—are as large as possible.

In the present work, a thorough investigation of evolution of microstructure and texture has been carried out to elucidate the evolution of texture and grain boundary character distribution (GBCD) during Equal Channel Angular Extrusion (ECAE) of some model two-phase materials, namely Cu-0.3Cr and Cu-40Zn. Texture of Cu-0.3Cr alloy is similar to that reported for pure copper. On the other hand, in Cu-40Zn alloy, texture evolution in α and β (B2) phases are interdependent. In Cu-0.3Cr alloy, there is a considerable decreases in volume fraction of low angle boundaries (LAGBs), only a slight increase in CSL boundaries, but increase in high angle grain boundaries (HAGBs) from 1 pass to 4 passes for both the routes. In the case of Cu-40Zn alloy, there is an appreciable increase in CSL volume fraction.