An investigation on the precipitates in T5 treated high vacuum die-casting AE44–2 magnesium alloy

Abstract

The AE44-2 magnesium alloy was fabricated via die-casting under high vacuum (denoted as HVDC-AE44-2 alloy). The microstructures and mechanical properties of the aged HVDC-AE44-2 alloys were investigated. It found that age strengthening can be achieved in the HVDC-AE44-2 alloys. This paper reports, the HVDC-AE44-2 alloys after aging at 200 °C for 12 h (T5), the hardness increased by ~8.8 HV (~14.0%), the yield strength (YS) and the ultimate tensile strength (UTS) increased by ~30.5 MPa (~20.4%) and ~22.6 MPa (~9.1%), respectively, while the increase in strength after aging was not accompanied by a significant loss in ductility (The elongation was 19.6% in the die casting. The elongation was 19.1% in aged at 200°C for 12h). It is found that the improved age hardening ability is closely related to the Al4Mn and Al11Mn4 precipitation during aging. Both the α-Mg and the Al11RE3 have crystallographic orientation relationships with the Al4Mn. The slipping of dislocations was impeded by the precipitates during tensile deformation at room temperature, and the <a> dislocations were accumulated around the precipitates, which is the reason for the increase of the HVDC-AE44-2 alloy strength.