ABSTRACT
Mg-9Al magnesium alloy is a sand casting alloy containing aluminum, zinc and manganese. Typically, it is used in aerospace and automotive casting applications particularly where there is no high temperature requirement. The microstructural changes after heat treatment have been presented. For the microstructure observation, an OLYMPUS GX71 metallographic microscope and a HITACHI S-3400N scanning electron microscope equipped with an electron dispersive detector EDS (VOYAGER of NORAN INSTRUMENTS) were used. Quantitative examination was conducted using the Met-Ilo and AnalysisPro® automatic image analysis programs. The Mg-9Al alloy in as-cast condition is characterized by a solid solution structure α-Mg with discontinuous and continuous precipitates of Mg17Al12 phase at grain boundaries. Moreover, the occurrence of Laves’ phase in the form of Mg2Si and precipitates of Mn5Al8 phase, has been provided. The relationship between the as-cast structure, heat treatment parameters and quantity of intermetallic phases Mg-9Al magnesium alloy was specified. After solution treatment a reduction of the number of Mg17Al12 phase precipitations was observed. Application of ageing treatment caused precipitation of discontinuous Mg17Al12 phase.
