Influence of extrusion temperature on microstructure and mechanical properties of Mg-4Y-4Sm-0.5Zr alloy

The solution-treated Mg-4Y-4Sm-0.5Zr alloy was extruded at temperatures from 325 °C to 500 °C. Dynamic recrystallization (DRX) completely occurs when the alloy is extruded at 350°C and above. The grains of the extruded alloy are obviously refined by the occurrence of DRX. The average grain size of the extruded alloy increases with increasing the extrusion temperature, leading to a slight decrease of the ultimate tensile strength (UTS) and the yield strength (YS). On the contrary, the UTS and YS of the extruded and aged alloy increase with increasing the extrusion temperature. Values of UTS of 400 MPa, YS larger than 300 MPa and elongation (EL) of 7% are achieved after extrusion at 400 °C and ageing at 200 °C for 16 h. Both grain refinement and precipitation are efficient strengthening mechanisms for the Mg-4Y-4Sm-0.5Zr alloy.