On the microstructure and mechanical property of as-extruded Mg–Sn–Zn alloy with Cu addition

Abstract

This work explored the effect of Cu addition on the microstructure characteristics and tensile properties of as-extruded Mg–8Sn–2Zn alloys. Results indicated that adding Cu caused the formation of MgZnCu phase with a face-center cubic structure (α = 0.7169 nm) and exhibited subtle grain refinement effect of the as-cast alloys. Moreover, the volume fraction of MgZnCu phase increased as Cu content increased. Appropriate Cu addition could refine the precipitates and increase the number density of precipitate of as-extruded alloys, which resulted in the refinement of grains and weakening of texture intensity. However, extensive addition of Cu increased the size of secondary phases, thereby resulted in weak grain boundary pinning effect and growth of dynamic recrystallized grains. Such grain growth might cause the growth selection of grains with the predominant orientation of extruded fiber texture. The as-extruded Mg–8Sn–2Zn–0.5Cu alloy exhibited the optimal yield strength of 365.9 MPa and ultimate tensile strength of 388.4 MPa. High strength values were expected due to the high number density of micron-sized broken MgZnCu and Mg2Sn particles, as well as nano-sized Mg2Sn precipitates and fine grains.