Strengthening effect of nano and micro-sized precipitates in the hot-extruded Mg-5Sn-3Zn alloys with Ca addition

In this study, enhancement of mechanical properties of Mg-5Sn-3Zn alloy was achieved by alloying with Ca, and the strengthening response due to coarse CaMgSn, nano and micro-sized Mg2Sn precipitates in hot-extruded Mg-5Sn-3Zn based alloys was reported. As the content of Ca increases, the amount of Mg2Sn and CaMgSn precipitates in Mg-5Sn-3Zn based alloys increases while the average particle size of those precipitates decreases. Mg2Sn phases in both micrometer and nanometer scale are observed in Mg-5Sn-3Zn alloys with and without Ca. Besides micro-sized and nano-sized Mg2Sn, coarse precipitates of CaMgSn are observed in Mg-5Sn-3Zn with Ca addition. By alloying with Ca, grains are refined and fiber {0002} texture in hot-extruded Mg-5Sn-3Zn based alloys is weakened. The Mg-5Sn-3Sn-1Ca alloys show the largest YS of 118 MPa, UTS of 275 MPa and elongation of 21.9%. Improvement in combined strength and ductility of Mg-5Sn-3Sn-1Ca alloys is attributed to less coarse CaMgSn precipitates, more and finer nano-sized Mg2Sn precipitates, and a weak {0002} fiber texture.