EFFECf OF A1P IN SOLIDIFICATION SEQUENCE OF AI-6Mg-3Si

摘要

In recent years, weight reduction of vehicle body has been required in the automobile industry. Aluminium alloy have characteristic of strength/weight ratio and excellent corrosion resistance. Therefore, the application of aluminium alloy have been expanded in the auto parts. Al-Mg-Si alloy has both of good strength and high ductility without heat treatment, which is attracting attention as new die-cast alloy. However, this alloy is hard to cast, hot-tearing is easily occured during solidification. Therefore, it becomes a problem in the manufacture of parts. We investigation the castability of Al-2~6%Mg-l~3%Si system alloy. As a result, the composition that hot-tear decresed was Al-6%Mg-3%Si alloy, because the composition of this alloy was close to quasi-binary eutectic of Al-Mg2Si In addition, it is found that hot-tearing was not occurred in the case of 0.04%Sr addition to Al-6mass%Mg-3mass%Si alloy. Eutectic Mg_2Si phase of Sr-free alloy was observed plate-like Mg_2Si having A1P nuclei. On the other hands, Eutectic Mg_2Si phase of 0.04%Sr addition alloy was the remarkable refinement and not present plate-like Mg_2Si. In this study, Al-6%Mg-3%Si alloy was water-quenching at any temperature, and the crystallization behavior of plate-like Mg_2Si phase having A1P nuclei was investigated in detail.