Effect of Erbium on the Microstructure and Mechanical Properties of Semi-Solid Al–7Si–0.4Mg Alloy

In this paper, semi-solid Al–7Si–0.4Mg–x erbium(Er) (x = 0, 0.1, 0.3, 0.5, 0.8 wt%) alloys are fabricated via electromagnetic stirring method. The effects of Er on the microstructures and mechanical properties of semi-solid Al–7Si–0.4Mg alloys are investigated. Results show that the eutectic π-phase is modified to fine sized Er-poor π-phase and primary α-Al is refined in semi-solid Al–7Si–0.4Mg alloys with the addition of Er. Meanwhile, the plate-like shape eutectic Si is transformed into fibrous eutectic Si with addition of Er, which has an excellent modification effect on the eutectic Si. Nucleation rate of the Er-poor π-phase is increased with a higher super cooling rate, which causes the refinement of primary α-Al and the modification of eutectic Si phase. With the addition of 0.3 wt% Er, semi-solid Al–7Si–0.4Mg alloys obtain the best tensile properties. The ultimate tensile strength and elongation values are 228 MPa and 10.4%, which is increased by 7% and 50% than Er-free alloy, respectively.