Effects of Zn on the microstructure, mechanical properties, and damping capacity of Mg-Zn-Y-Zr alloys

The influences of Zn on the microstructure, mechanical properties, and damping capacity of as-extruded (Mg-5%Y-0.6%Zr)_1−xZn_x (x = 2%, 4%, 6%, mass fraction) alloys were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, tensile testing, and dynamic mechanical analysis (DMA). The phase composition and microstructure of the alloys displayed evident variations with changes in Zn content. When the mass fraction of Zn changed from 2% to 6%, the phases mainly consisted of a long period stacking ordered (LPSO) X-phase (Mg₁₂YZn) and a W-phase (Mg₃Y₂Zn₃). Comparison of the mechanical properties and damping capacities of the different phases showed that the X-phase benefits the mechanical properties of the alloy without drastic impairment to their damping capacities. The damping capacities are discussed in terms of the Granato-Lücke theory and G-L plots.