Design strategy for microalloyed ultra-ductile magnesium alloys

This article describes a design strategy deployed in developing ultra-ductile Mg alloys based on a microalloying concept, which aims to restrict grain growth considerably during alloy casting and forming. We discuss the efficiency of the design approach, and evaluate the resulting microstructural and mechanical properties. After processing, the so-designed alloys ZQCa3 (Mg-3Zn-0.5Ag-0.25Ca-0.15Mn, in wt.%) and ZKQCa3 (Mg-3Zn-0.5Zr-0.5Ag-0.25Ca-0.15Mn, in wt.%) reveal very fine grains (10 m), high ductility (elongation to fracture of up to 30%) at moderate strength or high strength (ultimate tensile strength of up to 350 MPa) at reasonable ductility. These properties are explained based on thermodynamic modelling, microstructure analysis including transmission electron microscopy studies, and microstructural and mechanical testing after annealing, and are compared to a related commercial alloy (ZK31).