Age hardening in die-cast Mg-Al-RE alloys due to minor Mn additions

Die-cast Mg-Al-rare earth (RE) alloys are normally used in the as-cast condition without the application of heat treatment because it is a common perception that heat treatment will not provide benefit to these alloys. This paper reports, for the first time, that enhanced age hardenability can be achieved in die-cast Mg-Al-RE alloys with minor Mn additions. For example, the yield strength of Mg-4 wt%Al-3 wt%La alloy with 0.32 wt% Mn is increased by ~34 MPa (~26%) after ageing at 200 °C for 32 h (T5). The enhanced age hardenability is associated with the precipitation of nanoscale Al-Mn particles during ageing.