Al-Si 合金における共晶Si の微細化機構への考察

抄録

  Hypoeutectic Al-Si alloys are used for ductile die casting, which is the latest technology. Therefore, techniques to control the eutectic structure are required. However, because the Al-Si eutectic is an irregular eutectic, it is necessary to understand the mechanism of irregular eutectics. In this report, we attempt to discuss the reasons why Al-Si eutectic becomes irregular. By assuming that Si clusters caused by supercooling exist, it is possible to explain the branching and sticking (irregular eutectic) of the eutectic Si phase in the Al-Si alloy by the change in the temperature gradient G and growth rate V. Regarding the refinement process, the presence of Al₂Si₂Sr clusters caused by supercooling was assumed, and these were thought to be deposited on the non-faceted surface of the growing Si phase. These results suggest that the eutectic Si phase can be formed into a rod-shape by significantly increasing the twin density.