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

Abstract

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–4wt%Al–3wt%La alloy with 0.32wt% Mn is increased by ∼34MPa (∼26%) after ageing at 200°C for 32h (T5). The enhanced age hardenability is associated with the precipitation of nanoscale Al–Mn particles during ageing.