Precipitation Strengthening of a Mg-Al-Ca–Based AXJ530 Die-cast Alloy

Precipitation of the Al2Ca phase in the α-Mg phase of the Mg-Al-Ca–based AXJ530 die-cast alloy and the effect of precipitation hardening on the creep resistance were studied. Precipitation of the Al2Ca phase is suppressed in the die-casting process due to its high cooling rate, but precipitation was observed during subsequent isothermal heat treatments above 448 K. The precipitate has a disk-shaped morphology parallel to the basal plane of the α-Mg matrix phase and increases hardness by aging in the temperature range of 448 to 573 K. The creep resistance of the die-cast material at 448 K was improved by a factor of 1.5 ∼ 2, by a peak-age heat treatment at 523 K for 1 hour. Improvement in strength is limited by the low volume fraction of the precipitates; however, the precipitates are effective obstacles against dislocations gliding on nonbasal planes during creep deformation.