Insight into double twinning behavior of Mg–Gd rolled alloy at the nano scale: Role of micro-texture entropy

Abstract

101¯1}− {101¯2} double twinning is a classical twinning mode with diverse variants in magnesium and its alloys. However, its variant selection criterion and its influence on the mechanical behaviors are still in debate. In this study, we proposed a view of micro-texture entropy to elucidate the double twinning behavior during large strain rolling of Mg–1.5Gd (wt%) alloy. Combined with the high spatial resolution scanning electron microscopy-transmission Kikuchi diffraction (SEM-TKD) technique, the detailed microstructure and micro-texture of the double twins in early stage of evolution were detected, and new insight into the variant selection and evolution of double twins was obtained. The observations suggest that the nucleation events of different double twin variants are influenced by their micro-texture entropy, the variants with lower micro-texture entropy are preferred. While the growth stage of double twins is affected both by their micro-texture entropy and the geometric factors between the primary and secondary twin systems; the former will influence their growth potential and the later can affect their growth space. A novel {101¯1}− {101¯3} double twin was also triggered to release the high local stress concentration during large strain rolling process.