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

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 (alpha-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 degrees C, the solution time is 12h, the aging temperature is 200 degrees C, 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.