Deformation twinning in ultra-fine grained Ni at room temperature and low strain rate

Deformation twinning was observed in ultra-fine grained Ni at room temperature and low strain rate (1 x 1 0(-5)/s) in uniaxial tensile deformation, and especially observed in a single Ni wire. In this study, the grain boundary migration and deformation twins were confirmed by in-situ transmission electron microscopy and the post-fracture surface characterizations for ultra-fine grained Ni, indicating that the grain rotation and/or grain boundary migration result in a large number of misfit dislocations or partial dislocations at grain boundaries, which mediates nucleation of deformation twins. The deformation of the Ni single wire was dominated by deformation twinning and revealed the fine super-plasticity. In addition, the average slip line spacing is 8 nm from the tensile surface. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.