Effects of Mode of Deformation and Extent of Reduction on Evolution of {111}-Fiber During Cold Rolling of Ni-16Cr Alloy
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TION
THE deformation texture of pure nickel (Ni) shows metal-type texture having copper (Cu) as predominant component.[1] On the other hand, deformation texture of some Ni-based alloys such as Ni-Co,[1] Ni-Cr,[2] and Ni-W[3] display texture transition from Cu to Bs (Brass component) with the increasing alloying contents. This has been attributed to the lowering of stacking fault energy (SFE) with the increasing alloying contents, which in turn promotes twinning and shear banding.[4] The studies based on Taylor–Bishop–Hill theory have predicted that the major initial orientations play vital role in texture transition.[5,6] These initial orientations are rotated toward and within the b-fiber with the increasing cold-rolling reductions to arrive at stable end orientations. A few transitional components also appear during intermediate stages of rolling reductions. These are in fact related to both the initial as well as final
K.K. MEHTA is with the RDAQA (M), Defence Research and Development Organization, Kanchanbagh, Hyderabad 500058, India. R.K. MANDAL is with the Department of Metallurgical Engineering, IIT (BHU), Varanasi 221005, India. A.K. SINGH is with the Defence Metallurgical Research Laboratory, Hyderabad 500058, India. Contact e-mail: singh_ashok3@rediffmail.com Manuscript submitted August 11, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
texture, and play important role in the texture transition process. The development of {111}-fiber in fcc materials during moderate-to-high rolling reductions is an example of such a transitional texture.[7–10] It has been argued that the increase and subsequent decrease in the orientation density of {111}-texture components with the increasing rolling reductions represent a minor deviation in the evolution of Bs-type texture. It is assumed that the intermediate formation of {111}-fiber during moderate-to-high deformations assist in homogenization of strain distribution by activation of more number of octahedral slip systems and subsequent cross-slip. This in turn accommodates larger extent of cold deformation with nearly homogeneous distribution of strains throughout the material.[11] The changes in strain path/modes of rolling namely, unidirectional, cross, reverse, and clock rolling also influence the development of texture during deformation due to rotation, and reorientation of grains. This in turn affects the flow stress and recrystallization kinetics. During two- and multistep- cross-rolling modes, the change in strain path may cause strengthening/weakening of texture depending upon the local strains and texture rotations.[12–14] Most of the texture transition studies in different modes of deformation by cold rolling are related to aluminum alloys. Although some data are available for Ni-based alloys in the literature, these are by no means extensive particularly with respect to the mechanism of formation of transitional texture such as
{111}-fiber.[10,15–17] An attempt has therefore been made in the current study to explain the rotation of initial orientations and deve
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