Precipitation of DO19 type metastable phase in Mg–Sn alloy

• Formation of metastable precipitates in the binary Mg–Sn alloy has been investigated.
• Metastable DO19 type phase precipitates prior to precipitation of Mg2Sn phase.
• DO19 type precipitates lead to higher peak hardness than Mg2Sn precipitates.

Formation of metastable precipitates in the binary Mg–Sn alloy has been investigated in the present study. The Mg–1.5 at%Sn solid solution alloy exhibits two exothermic reactions during heating up to 673 K, where lower temperature reaction with onset temperature of 364 K corresponds to the formation of metastable DO19 type precipitates, while higher temperature reaction with onset temperature of 466 K to the formation of stable Mg2Sn precipitates. The comparison of aging behavior at 423 K and 473 K indicates that lower temperature aging at 423 K results in retardation of peak aging time, but higher peak hardness due to the precipitation of DO19 type phase.