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Mg-Al-Sn alloy system offers good combination of strength, ductility, castability and corrosion resistance for potential automotive structural applications. This report summarizes the micro structure and mechanical properties of two Mg-Al-Sn alloys, AT72 (Mg-7Al-2Sn1) and AT96 (Mg-9Al-6Sn), prepared using high pressure die casting process. The microstructure of as-cast Mg-Al-Sn alloys was investigated using computational thermodynamics modeling and experimental techniques. Both alloys show improved mechanical properties and excellent die castability compared with the conventional AZ91 (Mg-9Al-1Zn) and AM50 (Mg-5Al-0.3Mn) alloys. The AT72 alloy is currently used in developing large thin-wall die cast door inners and cast magnesium wheels.

The microstructure and mechanical properties of as-cast Mg-Al-Sn alloys have been investigated using computational alloy design and experimental approaches. The as-cast microstructure of Mg-Al-Sn alloys consists of α-Mg, Mg17Al12 and Mg2Sn phases. The volume fractions of Mg17Al12 and Mg2Sn phases increase with increasing Al/Sn contents, and show good agreement between computational thermodynamics modeling and the experimental results. Generally, the yield strength of as-cast alloys increases with Al/Sn alloying contents, while the ductility decreases. This study has confirmed an earlier development of Mg-7Al-2Sn alloy and led to a promising new Mg-7Al-5Sn alloy with significantly improved strength and ductility compared to commercial alloy AZ91 (Mg-9Al-1Zn).