Re-evaluation of the mechanical properties and creep resistance of commercial magnesium die-casting alloy AE44

Abstract

This paper presents a re-evaluation of the room temperature mechanical properties and high temperature creep resistance of magnesium die-casting alloy AE44 (Mg-4Al-4RE) in light of the influence of minor Mn addition. It is shown that the Mn-containing AE44 exhibits distinct age hardening response upon direct ageing (T5) due to the precipitation of nanoscale Al-Mn particles, as reported previously in a similar alloy. The T5 ageing leads to a significant improvement in strength with similar ductility. Consequently, the T5-aged AE44 has a remarkably better strength-ductility combination than most Mg die-casting alloys and even the Al die-casting alloy A380. Minor Mn addition is also shown to be critical for the creep resistance of AE44 whereas the influence of the RE constituent is not as significant as previously thought, which reaffirms that precipitation hardening of the α-Mg matrix is more important than grain boundary reinforcement by intermetallic phases for the creep resistance of die-cast Mg alloys. The findings in this work could provide new application perspectives for AE44, particularly in the automotive industry.