Mechanical and damping properties of thermal treated Mg-Zn-Y-Zr alloys reinforced with quasicrystal phase

The effects of annealing, T4 and T6 heat treatment on microstructure, mechanical properties and damping capacities of a quasicrystal-reinforced Mg-Zn-Y-Zr alloy (the ZWK3 alloy) were investigated in this study. The structural results show that the Mg0.97Zn0.03 phase could transform to Mg7Zn3 phase during annealing and only primary phase and the I-Mg3YZn6 quasicrystal phase exist in the T4 treated ZWK3 alloy. Further aging in T6 treatment precipitates a large amount of nanoscaled MgZn2 phase. The thermal treatment could improve the tensile strength of the ZWK3 alloy greatly, while a large reduction in elongation and high strain amplitude damping are obtained compared with that of the as-cast alloy. In spite of this, the damping values of three heat treated ZWK3 alloys all exceed 0.01, representing our studied alloys still belong to high damping magnesium alloys. Decrease of mobility of dislocations, resulting from tanglement and pinning, is responsible for damping decline. We also find that twins only observed in the T6 treated ZWK3 alloy could produce new damping sources besides dislocation.