The influence of minor Mn additions on creep resistance of die-cast Mg-Al-RE alloys

Magnesium alloys normally contain minor amounts (~0.3%) of Mn to achieve improved corrosion resistance by controlling the level of Fe during melting. It has been reported recently that minor Mn additions can significantly enhance the age hardenability of die-cast Mg-Al-RE alloys. This paper reports that minor Mn additions also have a remarkable influence in improving the creep resistance of die-cast Mg-Al-RE alloys. The secondary creep rate of Mg-4Al-3La alloy at 175 °C/75 MPa is reduced by more than three orders of magnitude (from 5.9×10-7 s-1 to 3.0×10-10 s-1) by the addition of 0.32% Mn. The improvement in creep resistance is associated with the dynamic precipitation of nanoscale Al-Mn particles during creep. The findings in this work shed new light on creep resistance of Mg-Al based alloys.