Microstructural evolution and age-hardening behavior of quasicrystal-reinforced Mg-Dy-Zn alloy

Microstructural evolution and age-hardening behavior of Mg-2Dy-6Zn (at%) alloy during solid-solution and aging treatment were investigated. The microstructure of as-cast alloy is composed of -Mg, Mg3DyZn6 (I) phase, Mg3Dy2Zn3 (W) phase, Mg(Zn,Dy) phase and a small amount of Mg0.97Zn0.03 phases. After solid-solution treatment (480 degrees C, 12h), all the I phases and most W phases dissolve into -Mg matrix and the remainder W phases transform into Mg(Dy,Zn) phase and MgDy3 phase. During aging treatment, I phase and small amounts of W phases co-precipitate from -Mg matrix, respectively. The alloy exhibits a peak hardness of HV 77.5 at 200 degrees C for 8h. The excellent age-hardening behavior of alloy is mainly attributed to the co-precipitation strengthening of I and W phases.