Akira Suzuki1, Jitsuhito Nakamura1 and Toshimasa Sakamoto1
1Central Research Laboratory, Kobe Steel, Ltd., Kobe
The present work was carried out so as to investigate the substructures of columnar grains in Al-Cu alloy ingots in connection with the growth conditions.
The change of substructures of columnar grains was observed in aluminium ingots under a high pressure applied during solidification. Further experiments were performed on Al-0.2, 1 and 2%Cu alloys, and it was found that columnar grains grown under a high pressure, 2,072 kg/cm2, exhibited a simpler morphology than those grown under the atmospheric pressure. And in Al-0.2%Cu ingots solidified under the atmospheric pressure, the columnar grains grew in a cellular dendritic manner in the ingot cast in the mold at 15°C, and in a dendritic manner in the mold at 500°C.
The above-mentioned change and difference in the substructures of columnar grains are hardly explainable in terms of growth parameter, G/V, where G is the temperature gradient in the liquid phase ahead of the freezing front and V is the growth rate of dendrite tips. However, taking G for the temperature gradient behind the freezing front, the dependence of growth morphology of columnar grains on G/V is consistent with the previously confirmed results.
Please do not copy without permission.