Effect of Er addition on the microstructural characteristics and compressive behavior of insitu Al-15 wt.% Mg2Si composites

The modification of Mg2Si is considered as a key parameter to improve the mechanical properties of Al-Mg2Si composites. In the present work, the effect of erbium (Er) on the microstructural charactristics and compressive behavior of cast Al-15 wt.% Mg2Si in situ metal matrix composite was studied. Microstructural examination was conducted using optical and scanning electron microscopy (SEM). The results showed that the size of the primary Mg2Si phase was reduced from 14 to 8.5 μm with the addition of 0.6 wt.% Er and the its morphology was modified from a coarse dendritic shape to a polyhedral shape. Through the addition of Er, the morphology of eutectic Mg2Si was also altered from coarse flake-like to a fine fibrous form. Besides, it was found that some Al3Er compound were formed during solidification. Compression test indicated that Er addition enhanced the compressive strength of the composite. The highest compressive strength was obtained for the 0.6 wt.% of Er-modified composite with 32% increase.