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.