Application of quasicrystalline particles as a strengthening phase in Mg-Zn-Y alloys

Fine-grained magnesium alloys reinforced by quasicrystalline particles were easily developed by thermomechanical processes for as-cast Mg-rich Mg-Zn-Y and Mg-Zn-Y-Zr alloys. The deformation behaviour of the alloys at room and high temperatures was investigated and compared with that of commercial AZ31, AZ61 and AZ91 alloys. The yield strength of the Mg-Zn-Y alloys, increasing with an increase of the volume fraction of the quasicrystalline phase, is relatively high due to the strengthening effect of the quasicrystalline particles. At high temperatures, the level of flow stress of the Mg-Zn-Y alloys is lower than that of commercial magnesium alloys due to the softness of the eutectic region, but the alloys exhibit much higher elongation since the large number of quasicrystalline particles in the Mg-Zn-Y alloys can effectively prohibit microstructural evolution of the alpha-Mg matrix during deformation. Icosahedral particles in the alloy are also stable against coarsening during deformation near the melting temperature of the eutectic due to their low interfacial energy, thereby forming a stable quasicrystalline particle/matrix interface. The stability of both the quasicrystalline particles and the microstructure of the Mg-Zn-Y alloys provides a large elongation with no void opening at the interface between the quasicrystalline particle and the alpha-Mg matrix. (C) 2002 Elsevier Science BM All rights reserved.