AlのTiによる結晶微細化の機構に関する研究

抄録

To provide sufficient evidence as to the mechanism of grain refinement of Al, Al-0.04%Ti alloy was solidified in a mold equipped with a horizontal barrier, by which a zone of very fine grains was found to exist only on the barrier and not under it. This is considered to be inconsistent with the nucleating agent theory and the peritictic reaction theory. When Al-0.15%Ti alloy was poured into a graphite mold at 750°C, very fine grains were obtained. The grain size increased markedly as the pouring temperature was increased to 900°C. However, the grains became refined when the molten surface was agitated during solidification. The mechanism of the grain refinement is considered to be dendrite remelting due to the temperature fluctuations in the mold in the early stage of solidification. It appears that solid particles, such as TiC, which have been considered as the nucleant of crystallization are trapped in the crystals by dendrite arms during solidification.