Effect of double aging and microalloying on the age hardening behavior of a Mg–Sn–Zn alloy

We have investigated the effect of double aging and microalloying on the age hardening behavior of a Mg–2.2Sn–0.5Zn alloy. The double aging at 473 K after pre-aging at 343 K lead to an increased peak hardness to more than 80 HV as a result of the refinement of the polygonal Mg2Sn precipitates by the heterogeneous nucleation at densely dispersed MgZn2 precipitates. The age hardening response of the Mg–2.2Sn–0.5Zn alloy was further enhanced by microalloying with 0.2Cu (at.%), 0.2Ca–0.2Ag–0.2Zr or 1.0Al. In particular, the peak hardness of the Mg–2.2Sn–0.5Zn–1.0Al alloy was 95 HV at 433 K, which was attributed to the synergy effect of the dispersion of the fine rod and polygonal Mg2Sn precipitates and solution hardening with Al.