Discontinuous long-period stacking ordered structures induced serrated twin boundaries in a Mg-Gd-Zn alloy

Abstract

Long-period stacking ordered (LPSO) structures can enhance the mechanical properties of magnesium alloys by impeding dislocation motion and hindering deformation twin. In this work, we reported serrated twin boundaries (TBs) induced by LPSO-mediated twin impedance in room-temperature-processed Mg-Gd-Zn alloy and characterized the formation mechanisms at atomic-scale. For the LPSO structures with discontinuous or random spatial distributions in the matrix, TB bypasses the discontinuous LPSO structures, forming the LPSO/TB (basal-prismatic, BP) interfaces. Zn-enriched misfit dislocations formed at the LPSO/TB interface and exerted interfacial pinning on TBs. Reactions of matrix basal dislocations with TBs generate twinning dislocations accompanied by emission of partial basal dislocations and formation of stacking faults (SFs) in twin domains. These SFs also exerted a pinning effect on the BP interface. The synergistic effect of these factors generates serrated $\left\{10\overline{1}2\right\}$ deformation twins and provides new insights into LPSO-twin interaction mechanisms.