Thermal Analysis and Microstructure of Al-12%Si-2.5%Cu-0.4%Mg Cast Alloy with Ce and/or La Rare Earth Metals

This article aims to investigate the modification response of the grain refined Al-12%Si-2.5%Cu-0.4%Mg alloy to rare earth metals addition with various La and/or Ce levels. Thermal analysis was used to evaluate the influence of cooling rate and rare earth element addition. Microstructure was examined using optical microscopy, image analysis and scanning electron microscopy. The results showed that 0.8% Cerium and 0.7% La brought about full modification of eutectic Si particles, while the addition of both 0.8 wt% La and 0.55 wt% Ce reduced the eutectic temperature by ~8.47 °C. The addition of Ce and/or La has a noticeable effect on decreasing the eutectic Si phase size (area and length) and aspect ratio and increasing the particle roundness and circularity. The Ce- and/or La- rich intermetallic compounds are detected such as Al_5.52Si_1.31(Cu_0.41, Ce_0.59)Fe_0.24, Al_5.51Si_1.36(Cu_0.4, Mg_0.1, La_0.5), Al_6.9Si_3.3(La_0.69, Ce_0.31) and Al_7.7Si_2.5Cu_0.75 La_0.98Ce_0.5and are believed to play a role in reducing the modification effect of both additions.