Thermodynamic predictions of Mg – Al – Ca alloy compositions amenable to semi-solid forming

Abstract

Abstract Thermodynamic prediction based on 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 on the solidification range 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 Al2Ca 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.