Studies on Magnesium Alloys–Properties and Potential for Automotive and Aerospace Applications

Abstract

Magnesium-based alloys have enormous potential for high performance structural applications due to their light weight combined with high specific strength, superior damping capacity, etc. Among the Mg-based alloys, AZ series cast Mg-alloys have been extensively studied and used for some structural components of automobiles, aircraft, and computers. AZ91 alloys show poor high temperature properties because Mg Al intermetallic has low melting point 17 12 o o(437 C), higher diffusivity in Mg matrix, coarsen at a faster rate and hence, unstable at temperature above 120 C. MgSn based alloys have been developed which showed superior high temperature properties to conventional AZ series Mg alloys. Studies have been conducted on conventional cast and rheocast Mg-5%Sn, Mg-8%Sn, and Mg-8%Sn-3%Al1%Si (TAS831) alloys. The microstructure of the conventional cast sample is typically dendritic in contrast to rheocast structure which is nearly globular. The microstructure of conventional cast Mg-5%Sn alloy showed three different phases such as primary α -Mg, precipitate phases β -Mg Sn and eutectic α -Mg at the grain boundary. In Mg-8%Sn-2 3%Al-1%Si alloy α -Mg, Mg Sn, Mg Al and Mg Si phases were observed. The mechanical properties of rheocast alloys 2 17 12 2 are significantly higher than those of the conventional cast alloys. After solution treatment the ductility of all the alloys are improved significantly. The room temperature tensile data of conventional cast alloys reveals ~ 10% improvement in UTS after 100 h aging as compared to as cast condition. The creep resistance in conventional cast TAS831 alloy is higher than the Mg-8%Sn alloy.