Modification of hypoeutectic Al-Si alloys with scandium

The present study was undertaken to investigate the effects of Sc on the modification of Al6Si0.25Mg alloy. The two levels of scandium used were 0.2 wt.% or 0.4 wt.%. For each treated condition, the mean shape factor of eutectic Si was determined to quantify the level of the modification effect. It was found that a Sc addition of only 0.2 wt.% modified eutectic Si by changing its morphology towards a rounded and fibrous shape. Zr, which is usually added together with Sc in wrought aluminum alloys, was also studied to observe any possible effect on modification. The results show that addition of Zr together with Sc increases the effectiveness of modification by Sc. Thermal analysis was applied to understand how Sc affects solidification. From the thermal analysis results, it was observed that Sc reduced the eutectic growth temperature, which is similar to the results from modification using Sr.