Influence of Sr and TiB on the Microstructure and Eutectic Temperature of Al-12Si Die-Cast Alloys

Abstract

In order to develop a new commercial Al-12% Si casting alloy with improved physical properties, we investigated the effect of adding Sr and TiB to the alloy. Al-12% Si alloys were prepared by die casting at 660 degrees C. The eutectic temperature of the Sr-modified Al-12% Si alloy decreased to 9 degrees C and the mushy zone region increased. The shape of the Si phase changed from coarse acicula to fine fiber with the addition of Sr. The addition of TiB in the Al-12% Si alloy reduced the size of the primary alpha-Al and eutectic Si phases. When Sr and TiB were added together, it worked more effectively in refinement and modification. The density of twins in the Si phase-doped Sr increased and the width of the twins was refined to 5 nm. These results are related to the impurity induced twinning(IIT) growth.