Effect of Ce Addition on the Thermal Conductivity and Mechanical Properties of Al-7Si-0.6Fe-0.5Zn Cast Alloy Treated by B/La/Sr Modification

In order to further improve the thermal conductivity and mechanical properties simultaneously of the base alloy (Al-7Si-0.6Fe-0.5Zn alloy) treated by B/La/Sr modification, the La content was further optimized in the B/La/Sr-modified process, and the Ce element was added into the melt treated by B/La/Sr modification to get higher improvement. For the B/La/Sr-modified alloys, when the content of La decreases from 0.15 to 0.05%, the thermal conductivity (lambda) and integrated mechanical properties index (Q) increase 3.1W/(m center dot K) and 21.1MPa, respectively. In the B/La/Ce/Sr-modified alloys, the lambda and Q increase simultaneously with the increase of the Ce content, reaching the maximum of 179.2W/(m center dot K) and 380.2MPa, respectively, when the Ce content reaches 0.5%, and then decrease simultaneously with the further increase of the Ce content. When the Ce content is not more than 0.5%, the morphology change of the Fe-rich phases is the main reason for the simultaneous improvement of the thermal conductivity and the mechanical properties of the B/La/Ce/Sr-modified alloys. When the Ce content is more than 0.5%, the precipitation of the needle flake-like Ce-rich phases and coarse flake-like Si phases is the main reason for the simultaneous deterioration of the mechanical properties and thermal conductivity.