Microstructure and heat-resistant property in Mg-3%Al-1%Si alloy castings

Magnesium alloys have the characteristic with high specific strength and lightweight property, it is widely used for auto mobile industry. Heat-resistant magnesium alloy is focused as a suitable material for weight reduction of the engine and power train parts in automotive field. In this study, microstructure and heat-resistant property in Mg-3mass%Al-1mass%Si alloy castings produced by permanent mold casting were investigated by optical microscope (OM), scanning electron microscopy (SEM) and measuring of bolt load retention at 423K. The specimens were prepared which simulated the bolt conclusion of true parts and investigated the change of the residual axis power when compressive stress was applied at a high temperature. As a result, bolt load retention of Mg-3mass % Al-1mass % Si (AS31) alloy was higher compared with conventional Mg alloy (e.g. AZ91 and AM60 alloys).