Simultaneous reductions of dislocation and twin densities with grain growth during cold rolling in a nanocrystalline Ni-Fe alloy

Microstructures in nanocrystalline Ni-Fe alloys during cold rolling are quantitatively investigated by synchrotron high-energy X-ray diffraction. It is found that rolling leads to an obvious reduction in the densities of both dislocations and twins and an increase in crystallite size. A huge dislocation flux flows through the grains during rolling, even though only a small fraction remains in the specimen after rolling. A mechanically induced relaxation of the initial high-excited state of materials is revealed. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.