Effect of Change in Strain Path During Cold Rolling on the Evolution of Microstructure, Texture And Hardness Properties of Nickel With Extremely Coarse Initial Grain Size

Chaudhary, Vijay Prakash and Bhattacharjee, Pinaki Prasad (2012) Effect of Change in Strain Path During Cold Rolling on the Evolution of Microstructure, Texture And Hardness Properties of Nickel With Extremely Coarse Initial Grain Size. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

The effect of strain path change during cold rolling on the evolution of microstructure, texture and hardness properties of high purity nickel (~99.7%) with extremely coarse starting grain size (~800 μm) has been studied in the present work. For this purpose two different rolling routes, namely, unidirectional cold rolling (UCR) and cross cold rolling (CCR) are investigated in the present work. The rolling direction is kept constant throughout the deformation process in UCR route but during CCR processing the rolling direction and the transverse direction are mutually interchanged in every consecutive pass by rotating the material around the normal direction. Nickel sheets were deformed up to 90% reduction in thickness using the two processing routes. UCR processing route results in a microstructure having both lamellar and highly fragmented regions and pure metal or copper type deformation texture having strong presence of S, Cu and Bs orientations. The CCR processed microstructure also appears to be fragmented and locally sheared regions could be easily identified. The texture of CCR processed material is characterized by strong presence of the S component. The two processing routes are found to affect the hardness properties significantly. The hardness of UCR processed materials increases with increasing thickness reduction due to cold rolling which may be explained by the usual strain-hardening behavior. In contrast, the hardness of CCR processed material increases up to 65% deformation and thereafter it is found to decrease.

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