Local and global deformation behaviour in rolled pure magnesium sheets at room temperature under different strain rates

Abstract

In this paper, deformation behaviour of a rolled pure Mg sheet at room temperature was explored at quasi-static strain rates (10−4, 10−3 and 10−2·s−1) under the context of microstructural and textural observation. Tensile tests with an aid of digital image correlation (DIC) were performed along a rolled (RD) and transverse (TD) direction resulting in ~3%, ~4% strain and fracture. The microstructure and texture of the initial and deformed samples were characterised by EBSD and OM measurements. Mechanical properties including r-value and strain rate sensitivity (SRS) were evaluated and analysed with twinned area fraction. The results showed an obvious anisotropy and rate dependence in mechanical properties and deformation modes. The higher flow stress in TD samples was effectively elucidated by the Schmid factor analysis. The origin of the early fracture in RD samples was discussed with respect to the SRS and strain distributions where RD samples displayed a steep and narrowed strain localisation. Interestingly, TD samples showed a reversed dependence of twin activity at the fractured samples and total elongation on strain rate. Instead of tension twinning, basal <a> slip induced width strain in TD samples is likely to promote homogeneous lateral deformation which may eventually lead to the higher elongation in TD samples.