Microstructure and super high strength of cast Mg-8.5Gd-2.3Y-1.8Ag-0.4Zr alloy

A super high strength Mg-8.5Gd-2.3Y-1.8Ag-0.4Zr alloy with good ductility was developed using an ordinary casting technique and heat treatment. After the solution treatment at 500 °C for 10 h and subsequent ageing at 200 °C for 32 h, the room temperature TYS, UTS and elongation of the cast-T6 alloy was 268 MPa, 403 MPa and 4.9% respectively. Ag additions produce improved solid solution strengthening and enhanced the age hardening response. The enhanced age hardening response was attributed to the basal nano-scale plate precipitates, which were not observed in the Ag-free alloy, as well as the refinement of β′ phase. The co-precipitation strengthening produced by the β′ phase and the plate-like precipitates was deemed to be the largest contributor to the strength of the cast-T6 alloy.