材料期刊网

Thermodynamic prediction based oil a two-stage simulation has been carried out to investigate the composition range of Mg-Al-Ca alloys amenable to semi-solid forming. The results show that increasing the solute elements decreases the temperature sensitivity, but their effects oil the solidification ran-e are greatly different. In some Mg-Al-Ca alloys, the highest knee point in the liquid fraction vs. temperature Curve IS generated by the formation of Al(2)Ca phase. Several critical sections of the Mg-Al-Ca ternary system are also given. The criteria for semi-solid formability are identified and a range of compositions for Mg-Al-Ca alloys are evaluated in relation to these criteria. By comparing with A356 alloy and AZ91 alloy, a typical Mg-Al-Ca alloy AC74. is predicted to exhibit good semi-solid formability comparable to A356 and much better than AZ91.