Effect of Sr Content on Creep Properties of Mg-4Al-2Sn Alloy

摘要

Creep rupture properties and microstructures of an as-cast Mg-4Al-2Sn alloy with and without Sr contents (1 wt% and 2 wt%) were investigated. Creep rupture tests were performed at 150 °C and 200 °C at 50 MPa and 70 MPa. The microstructure of the Mg-4Al-2Sn alloy initially had Mg_(17)Al_(12) and Mg_2Sn phases. The addition of Sr resulted in the formation of a ternary MgSnSr phase. Creep strength increased with an increasing Sr due to thermally stable MgSnSr precipitates, which suppressed coarsening of the Mg_(17)Al_(12) precipitates during creep. Scanning electron microscopy showed that Mg_(17)Al_(12) phases at the grain boundaries are the starting point of void initiation, the cracks propagated along the grain boundaries. However, the MgSnSr phase interrupted crack propagation.