Deformation of soft crystals in precision polishing

Grinding/polishing soft materials typically introduces a layer with residual stresses, which impedes the examination of the original deformation states. In this work, precision polishing procedures consisting of mechanical polishing and electrochemical polishing were used to obtain residual-stress-free surfaces in an annealed copper polycrystal and a copper single crystal. For the polycrystal, mechanical polishing followed by electrochemical polishing were used to show the grain structure and etching pits. The polished single crystal was analysed by electron backscatter diffraction (EBSD) technique to reveal the lattice rotation field related to the original deformation state induced by wedge indentation. Specifically, the geometrically-necessary dislocation density was calculated based on the in-plane crystal lattice rotation angles. The precision polishing makes the observation of the effective slip systems as predicted by the crystal plasticity theory possible. The precision polishing also helps reveal the deformation instability in the indented copper single crystal by sharp indenters. Copyright © 2009, Inderscience Publishers.