The influence of mischmetal and tin on the microstructure and mechanical properties of Mg–6Zn–5Al-based alloys

The influence of the addition of mischmetal (MM) and tin (Sn) (total content of mischmetal and tin = 4 wt.%) on the microstructure, aging behavior and mechanical properties of Mg–6Zn–5Al-based alloys has been investigated. The microstructure of the as-cast alloys consists of α-Mg, Mg32(Al, Zn)49, Al2Mg5Zn2, Mg2Sn and Al2MMZn2 phases, and the morphology of these intermetallic phases varies with different MM and Sn additions. The hardness vs. aging time curves of all the alloys exhibit two peaks, and nanocrystalline Mg32(Al, Zn)49 and Mg2Sn precipitates are formed in the matrix. The alloys exhibit high tensile properties at 200 °C, which indicates that the high thermal stability of the Mg32(Al, Zn)49, Mg2Sn and Al2MMZn2 phases can hinder dislocation and grain-boundary sliding at elevated temperatures.