Abstract: Evolution of microstructure and mechanical properties of WE43 rare earth magnesium alloy under different heat treatment processes was studied in order to optimize the heat treatment process. The results show that the as-cast microstructure of the WE43 rare earth magnesium alloy is relatively uniform, with equiaxed grains of average grain size of 40 μm. During the process of solidification, the divorced eutectic forms along the grain boundaries. After solution treatment at 520 ℃ for 8 h, for the structure of the divorced eutectic, the number and morphology change significantly, the dendrite segregation is basically eliminated, and there are still a small amount of undissolved second phases on the grain boundary. After aging at 230 ℃ for 8 h, the amount of rare earth second phase increases, and dot-like dispersed rare earth phases are precipitated inside the grains. After aging at 250 ℃ for 16 h, the hardness of the alloy reaches its peak, the hardness of the alloy then decreases gradually as the ageing time extending. After solution treatment, the tensile strength of the WE43 rare earth magnesium alloy is about 162.59 MPa, and the elongation after fracture is about 5.0%, while after aging at 250 ℃, its tensile strength is significantly increased, and the elongation after fracture is about 4%.

Key words: WE43 magnesium alloy, divorced eutectic, microstructure, solution treatment, mechanical properties