サクシノニトリル‐アセトン系有機モデル合金のデンドライト成長

Abstract

Unidirectional solidification experiments of a model alloy of succinonitrile (SCN)-acetone that is a transparent organic compound and is available for a direct observation were performed in order to clarify the solidification process of binary alloy. The dependences of primary arm spacing (DAS1) of dendrite and secondary arm spacing (DAS2) on the growth speed of a crystal were studied. The sample, heareafter called as the cell, was inserted into the gap of the two slides (26 mm×76 mm×1.3 mm each), of which distance was 200 μm. The cell was pulled at a constant speed V toward the low temperature side under the fixed temperature gradient (1 K/mm). Changing pulling speed of the cell controlled the growth speed of the crystal. The composition of the examined samples is SCN-1.9 mass% acetone and SCN-6.0 mass% acetone. DAS1-V relationship was studied for the 1.9 mass% case only and found to be in proportional with the growth speed V-1/2. This is almost the same as that of unidirectional solidification of aluminum-(0.1-6.9) mass%Si alloy. DAS2 of 1.9 mass% and 6.0 mass% changed with growth speed as V-1/3. However, when growth speed increased, DAS2 of 1.9 mass% and 6.0 mass% decreased more than the V-1/3 relationship. DAS2 of 6.0 mass% separated from the curve of V-1/3 earlier than that of 1.9 mass%.