급속응고된 Al-Si 합금분말의 미세조직과 공정 Si 의 성장방향

On the Micro-structures of Rapidly Solidified Al-Si Alloy Powder and Growth Direction of Eutectic Silicon

Al-Si alloy powder produced by the gas atomizer showed fine eutectic structure between ${\alpha}-dendrites$, that was grown by coupled growth, and there remained small amount of ${\alpha}$ in Al - 20 wt% Si alloy. The morphology of Si in the eutectic structure was largely influenced by the recalescence caused by solidification latent heat, and that was thought to be due to decrement of the surface energy of Si. In modified eutectic Si by rapid solidification, fine twin about $0.01\;{\mu}m$ was observed and growth direction of eutectic Si was <112>. This fact implied that the growth mechanism of eutectic Si in rapid solidification was related to TPRE mechanism. Due to rapid solidification Si was soluble in ${\alpha}-phase$ in Al - 12.6wt%Si alloy up to about 3.4wt%, and the solubility of Si in ${\alpha}-phase$ reaches the equilibrium solubility stare after 60min, holding when it was held isothermally at $253-296^{\circ}C$.