Effect of Rare Earth Er on Microstructure and Mechanical Properties of Cast Al-Si-Mg Alloy
It is well known that Al-Si-Mg alloy can form Chinese script eutectic Mg2Si and large blocky primary Mg2Si phases. In this paper, the microstructures and mechanical properties of cast Al-18Si-10Mg-xEr (x=0, 0.3, 0.5, 0.8 and 1.0 wt.%) alloy were investigated. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) with wavelength dispersive spectroscopic (WDS). The results show that the morphology of primary Mg2Si changed from large block or Chinese script-like to fine block with increasing of Er contents from 0.3% to 1.0%., and the morphology of eutectic Si phases transformed into fine coral-like fibrous structure and the size of eutectic Si dramatically decrease. The mechanical properties were researched by tester with different concentration of rare earth Er. It was found that the ultimate tensile strength and hardness increased by 32.1% and 21.4%, respectively.