Microstructure-Property Relationships in an Erbium-Modified Al-Si-Mg Alloy

The effect of erbium (Er) addition at various weight percentages (0-0.6 wt.% at an interval of 0.2) on the microstructural features, tensile properties and wear behavior of as-cast Al-7.5Si-0.5Mg alloy were evaluated. The microstructure of the specimens was examined by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The obtained results clearly demonstrated that the incorporation of erbium decreased the α-Al grain size and eutectic Si, and altered the Si morphology from plate to semi-globular. Further addition of erbium (> 0.2 wt.%) did not alter the eutectic morphology and size. Moreover, the Al3Er phase was also observed in the eutectic region after modification. Out of the erbium contents used, 0.2 wt.% erbium showed the best influence on the tensile and wear properties. Compared with those of unmodified specimen, the values of ultimate tensile strength and elongation were enhanced by 31 and 39%, respectively through 0.2 wt. % erbium addition. Additionally, a remarkable enhancement in the wear properties was observed with the addition of 0.2