A micro-alloyed Mg-Sn-Y alloy with high ductility at room temperature

Here, Mg-0.4 wt%Sn based alloys containing different Y contents, Mg-0.4Sn-xY (x = 0, 0.7 and 2.0 wt%) alloys, were extruded into the sheets to systemically investigate the role of Y element on the microstructure, texture and mechanical properties of extruded Mg-0.4Sn alloy. We found that, with the Y addition, the average grain size gradually was reduced and the typical basal texture was transformed into the splitting one tilted to the extrusion direction. Moreover, the evidence of low number density and rough grain boundary cracks after tension indicated the strengthening in grain boundary cohesion with the Y addition. Besides more basal  slips, the activation of prismatic  slip and high intergranular strain propagation capacity were observed, which efficiently accommodated the sheet strain at room temperature. Those mentioned key factors contributed to the high room-temperature ductility of Mg-0.4Sn-0.7Y sheet. However, the formation and coarsening of Sn3Y5 and MgSnY phases were increasingly severe with increasing the Y addition to 2.0%. Those coarse secondary phases served as crack sources during tension deteriorating the ductility of Mg-0.4Sn-2.0Y sheet at room temperature. Therefore, we concluded that Y micro-alloying provided a new insight to achieve a superior room-temperature ductility of Mg-0.4Sn sheet.