Effects of Sr Addition on the Crystalized Phase in Al-6%Mg-3%Si Alloy

Abstract

  The effects of large amounts of Sr addition on the solidified structures and hot tearing of Al-6mass%Mg-3mass%Si alloys cast into the I-beam shaped mold were investigated by OM, SEM-EDS observations. The hot tearing of 0.04mass%Sr added alloy was less than Sr free alloys, due to the refinement of secondary crystallized eutectics, such as Mg₂Si and α-Al phases. On the other hand, when the Sr content in Al-6mass%Mg-3mass%Si alloys was above 0.04mass%, the area fraction of the hot-tearing region increased. This tendency for the hot tearing region to increase is caused by the crystallization of the Al-Si-Sr intermetallic compound. These findings suggest that the reasons for the increase in hot-tearing with the addition of large amounts of Sr affect the time of occurrence of two types of compounds (fine plate and coarse plate), the difference in their concentrations and frequency of occurrence.