Microstructural evolution and the role of interfaces in Mg-Zn-Y alloys with high strength and formability

Composites consisting of a quasicrystalline, icosahedral phase (I-phase) and ductile α-Mg can be fabricated by controlling the alloy composition in the Mg-Zn-Y alloy system. The I-phase in Mg-Zn-Y alloys shows a variation in structural order from a well-ordered icosahedral phase to a 1/1 rhombohedral approximant phase. The structural change in the icosahedral phase can be explained by microdomain formation due to compositional change during solidification. The characteristic of strong bonding between icosahedral particles and the α-Mg matrix indicates that the structural change from I-phase to crystalline phase is not discontinuous, but gradual. The interface layer of α-Mg with several nm thickness preserves an orientational relationship with the I-phase, although the remaining α-Mg shows a different orientation due to plastic deformation during deformation (rolling process). Such a strong interface can provide an excellent combination of high strength and formability in Mg-based alloys, enabling application as lightweight structural parts.