Enhanced age-hardening response and compression property of a Mg-7Sn-1Ca-1Ag (wt.%) alloy by extrusion combined with aging treatment

The age-hardening response and compression property of a Mg-7Sn-1Ca-1Ag (wt.%) alloy are improved by extrusion combined with aging treatment (abbreviated as extruded-aged). The corresponding microstructure evolution was investigated and discussed in detail. The results show that the average grain size of alloy was refined obviously from ∼54.6 μm to ∼3.2 μm by extrusion at 320 °C and the refinement of CaMgSn phase is also exhibited. Extrusion process promotes the precipitation of Mg2Sn and Mg54Ag17 phase and more precipitates of Mg2Sn phase exists in the extruded-aged alloy. As a result, age-hardening response and compressive strength are significantly enhanced in the extruded-aged Mg-7Sn-1Ca-1Ag alloy. The peak-aged hardness and ultimate compressive strength (UCS) of extruded-aged Mg-7Sn-1Ca-1Ag alloy are 95.2 HV and 482 MPa, respectively, both of which are obviously higher than that of as-aged and as-extruded alloys. This is mainly attributed to the grain refinement, formation of Mg54Ag17 phase and the increased content of finer Mg2Sn precipitates. Moreover, it was found that an obvious yield behavior occurs in compressive engineering stress versus strain of extruded and extruded-aged alloys, which is mainly attributed to the basal texture caused by extrusion and high value of Schmid factor, leading to the easy formation of {10-12} twinning in the extruded-aged alloy during compression along the extrusion direction.