Influence of Erbium Addition on the Microstructural Evolution and Tensile Properties of Al/Mg2Si in-situ Metal Matrix Composites

This study deals with the effects of Erbium (Er) addition on the microstructural evolution and tensile properties of Al-Mg2Si in-situ metal matrix composites. The morphology of primary Mg2Si and eutectic phases were observed in detail using an optical microscope and scanning electron microscopy (SEM). The results showed that the increase of Er content has a slight effect on the size and morphology of primary Mg2Si phases, but the eutectic structure evolves from the coarse structure into the fine one. Also, with Er addition, the eutectic mixtures of Al and Mg2Si with fibrous morphology have been developed instead of the flake-like Al-Mg2Si eutectic microstructure. Meanwhile, the Al3Er phase was observed in the samples containing Er. The ultimate tensile strength (UTS) of the composite changes under the various contents of Er. The maximum strength was found at 0.6 wt.% Er with the fine eutectic microstructure. The study of SEM micrographs from the fracture surface of composites revealed that Er addition changes the fracture mode from brittle to ductile one with fine dimples. The mechanism of microstructural evolution was discussed in detail.