Structure and mechanical properties of cast quasicrystal-reinforced Mg-Zn-Al-Y base alloys

The structure and mechanical properties of Mg-Zn-Al-Y base cast alloys containing an icosahedral quasicrystal phase (i-phase) as a main strengthening phase were investigated. Mg-8Zn-4Al-xY base bulk alloys containing the i-phase were prepared by casting into a copper mold at moderate cooling rates. The Y addition was effective for decreasing the size of the i-phase and the increasing the homogeneity of its dispersed state. The mechanical properties examined by compression tests at room temperature were much superior to those of a conventional AZ91 Mg alloy. The creep tests at elevated temperatures indicated a promising high temperature creep resistance of the quasicrystal-reinforced Mg-Zn-Al-Y cast alloy. The strengthening mechanism was also discussed.