Effect of Heat Treatment on Microstructure and Mechanical Properties of Mg-5Sm-0.6Zn-0.5Zr Alloy

Abstract

The effect of different heat treatment processes on the microstructure and mechanical properties of the as-cast Mg-5Sm-0.6Zn-0.5Zr alloy was investigated by orthogonal test. The results show that the as-cast Mg-5Sm-0.6Zn-0.5Zr alloy mainly consists of magnesium matrix (α-Mg) and eutectic second-phase; the order of influence of each factor on the average grain size is:solution time > aging temperature > aging time; the effect order of each factor on the tensile strength of the alloy is:aging temperature > solution time > aging time; the influence order of each factor on the elongation of the alloy after fracture is:solution time > aging temperature > aging time. The optimum heat treatment process with good comprehensive mechanical properties is as follows:the solution temperature is 540℃, the solution time is 12h, the aging temperature is 200℃, the aging time is 10h. The analysis of fracture morphology shows that the fracture mode of the as-cast alloy is quasi-cleavage fracture; the fracture modes of the aged alloys are complex, including quasi-cleavage fracture, cleavage fracture and intergranular fracture.

Keywords

• Mg-Sm-Zn-Zr alloy
• heat treatment
• orthogonal test
• microstructure
• mechanical property