Effect of Mg-based spherical quasicrystals on microstructure and mechanical properties of AZ91 alloys

To lay theoretical foundations for room and elevated temperature application of AZ91 magnesium alloys, microstructure and mechanical properties of AZ91 magnesium alloys strengthened by Mg-based spherical quasicrystalline phase have been investigated using XRD, SEM, TEM, hard-meter and impact testing machine. The experiment results show that macro-hardness and impact toughness of AZ91 magnesium alloys were improved a lot as the addition level of spherical quasicrystal containing Mg–Zn–Y–Mn master alloy increased; while adding 5.1wt.% spherical quasicrystal containing master alloy, impact toughness of AZ91 matrix composites reached the peak value, 15.3Jcm−2, which was about 252% as many as that of AZ91 master alloy. Majority of β-Mg17Al12 phase dissolved when spherical quasicrystal particles remained stable after 28-h T4 solution treating. Small dimples on fracture surface by impact of AZ91 magnesium alloy strengthened by quasicrystal particles exhibited the feature of ductile fracture.