Microstructure–grain orientation relationship in coarse grain nickel cold-rolled to large strain

The relationship between crystallographic orientation and the deformation microstructure formed during cold-rolling to high strains (up to ɛvM = 4.5) has been investigated. The starting material was Ni (99.96% purity) with a coarse initial average grain size (approximately 500 μm). Microstructural characterization was carried out using a combination of electron channeling contrast imaging and electron back-scatter diffraction orientation mapping. An orientation dependence of the deformation microstructure was observed even at the highest strain examined. A large increase in the average boundary misorientation is found at strains above ɛvM = 1.8 for regions with the {1 1 2}〈1 1 1〉 and {1 2 3}〈6 3 4〉 orientations. This increase accompanies the structural transition from a medium strain microstructure to a high strain lamellar microstructure. In contrast, the average misorientation in regions of {1 1 0}〈1 1 2〉 orientation increases only slowly even up to the highest strain examined.