Microstructure and strengthening mechanism of Mg-5.88Zn-0.53Cu-0.16Zr alloy solidified under high pressure

Mg-5.88Zn-0.53Cu-0.16Zr (wt.%) alloy was solidified at 2-6 GPa using high-pressure solidification technology. The microstructure, strengthening mechanism and compressive properties at room temperature were studied using SEM and XRD. The results showed that the microstructure was refined and the secondary dendrite spacing changed from 35 mu m at atmospheric pressure to 10 mu m at 6 GPa gradually. Also, Mg(Zn,Cu)(2) and MgZnCu eutectic phases were distributed in the shape of network, while under high pressures the second phases (Mg(Zn,Cu)(2) and Mg7Zn3) were mainly granular or strip-like. The solid solubility of Zn and Cu in the matrix built up over increasing solidification pressure and reached 4.12% and 0.32% respectively at 6 GPa. The hardness value was HV 90 and the maximum compression resistance was 430 MPa. Therefore, the grain refinement strengthening, the second phase strengthening and the solid solution strengthening are the principal strengthening mechanisms.