Enhanced microstructural stability and mechanical properties of the Ag-containing Mg–Gd–Y alloys

Abstract The effect of 0.5, 1 and 1.5 wt% Ag addition on the microstructural evolution, thermal stability and mechanical properties of an Mg–5 wt% Gd–1 wt% Y (GW51) alloy was investigated. The as-cast microstructure of the base alloy consisted of the Mg5(Gd,Y) phase in the α-Mg matrix. The obtained results revealed that Ag addition refines the dendritic microstructure of the base alloy, promotes the formation of the new Mg16Gd2YAg phase, and increases the volume fraction of the Mg5(Gd,Y) particles. These events resulted in improved hardness, strength, and microstructural stability of the Ag-containing alloys in the as-cast condition and after prolonged exposure to high temperature. The superior mechanical properties of the quaternary alloys over those of the tertiary alloy at low and high temperatures stems from the solid solution hardening effect of Ag, presence of the thermally stable Mg16Gd2YAg particles, and higher volume fraction of the Mg5(Gd,Y) particles. These particles can slow down the grain growth during exposure to high temperature, enhancing the stability and strength of the alloys at both room and high temperatures.