Achieving remarkable enhancement of yield strength and high ductility in a fine-grained Mg-6Zn-0.2Ca alloy via rotated hard-plate rolling

Abstract

Developing Mg alloys with high strength-ductility synergy presents a major challenge. In this work, a novel Mg-6Zn-0.2Ca alloy prepared via rotated hard-plate rolling (RHPR) exhibits a simultaneous high yield strength (YS) of ∼268 MPa and ductility of ∼22%. The RHPRed alloy features a fine-grained structure containing high-density low angle boundaries (LAGBs) and densely distributed nano-coherent precipitates, contributing to a remarkable improvement of YS (∼82 MPa) in comparison to the conventional rolling counterpart, while homogenizing tensile deformation. In the RHPRed alloy, the presence of ellipse-shape texture and grain-boundary disclinations adjacent to LAGBs promotes the activity of pyramidal <a> and <c + a> slip that governs the high ductility. The current work demonstrates the essential role played by high-density LAGBs and nano-coherent precipitates to the high strength-ductility synergy, which may provide insights into microstructural control strategy towards superior performance of Mg-Zn-Ca alloys.