Role of Y on the microstructure and mechanical properties of Mg-Gd-Zr alloy

The influence of Y on the microstructure and mechanical properties of Mg-4Gd-0.5Zr alloy is investigated. The results show that by increasing the Y content from 0 to 1.2 wt%, the grain size gradually reduces in both as-cast and as-extruded state, whilst the maximum texture intensity noticeably decreases. In addition, nanoscale particles of Mg24(Gd, Y)5 phase start to precipitate at relatively high Y content. The designed Mg-4Gd-0.5Zr-xY (x = 0, 0.5, 0.8 and 1.2 wt%) alloys exhibit exceptional ductility and moderate strength. As increasing Y content from 0 to 1.2 wt%, the elongation of Mg-4Gd-0.5Zr-based alloy decreases slightly from 44.6% to 39.0% along the extrusion direction, while the yield strength substantially increases from 87.9 to 134.1 MPa. The main strengthening mechanisms are demonstrated to be solid solution strengthening in combination with the grain refinement. Furthermore, the exceptional ductility maintained in Y-containing alloys is found to closely correlate with the activation of pyramidal slip.