Microstructure and heat resistance of Mg–Al–Zn alloys containing metastable phase

In this research microstructural studies have been made on cast specimens of AZ91 base alloys containing various amounts of Zn. As the amount of Zn addition increased up to 2%, any new Zn-containing phase did not appear while the Zn content in Mg17Al12 phase continuously increased. A quasi-crystalline phase started to form at Mg17Al12 phase when the added Zn content was about 3 wt.%. The tensile strength and elongation of the alloys at 175 °C were observed to increase significantly with increasing Zn content. The quasi-crystalline phase was found to be stable up to 300 °C, based on scanning electron microscopy examinations of the specimens heated at different temperatures for 24 h.