Effect of Cu Addition on the Microstructure and Mechanical Properties of an As-Extruded ZK60 Alloy

The effects of copper (Cu) addition on the microstructure and mechanical properties of ZK60 alloy were investigated using an optical microscope (OM), a scanning electron microscope (SEM), and electron backscatter diffraction (EBSD) and by performing tensile tests of indirect-extruded ZK60 alloys with 0.5, 1.0, and 1.5 wt% Cu contents. The results revealed that the as-extruded ZK60 alloy had a bimodal grain structure composed of fine recrystallized grains and coarse unrecrystallized grains. The homogeneity of the microstructure was increased by Cu addition due to the promotion of dynamic recrystallization (DRX) by particle stimulated nucleation (PSN) at the Mg-Zn-Cu particles. This enhanced DRX behavior resulted in the reduction of the average grain size and weakening of the basal fiber texture of the as-extruded alloys. The yield and tensile strengths were improved by the Cu addition owing to the decreased grain size and increased number of particles, while the elongation was decreased due to the hard Mg-Zn-Cu particles.