Effect of Heat Treatment on Microstructures and Mechanical Properties of Mg–5.5Gd–3.5Nd–0.5Zn–0.4Zr Alloy

In this study, we developed a new kind of high-strength Mg–5.5Gd–3.5Nd–0.5Zn–0.4Zr (wt%) alloy. Microstructures and mechanical properties of this new kind of alloy under different heat treatment conditions have been investigated. The as-cast alloy was composed of α-Mg matrix, discontinuous α-Mg + Mg 5 Gd eutectic phases, needle-like Mg 12 Nd phases, spherical α(Zr) particles, and cuboid-shaped (Gd, Nd)H 2 phases within α-Mg grains. Rod-like Zn 2 Zr 3 phases were formed and unevenly distributed inside the α-Mg matrix after solution treatment. Thin-plate β′ phases precipitated after aging at 205 °C for 24 h. The T6-treated alloy exhibited excellent tensile properties up to 250 °C. The dislocation cross-slip was activated when tensile temperature increased to 300 °C, which resulted in the largely decreased strength and increased elongation.