双ロール法急速凝固プロセスの冷却特性

抄録

The microscopic solidification structure of Pb-Sb eutectic alloy ribbons prepared by the twin-roll rapid solidification process has been examined to understand cooling characteristics of the process. The result shows that the average size and the area ratio of globular structure mainly consisting of Sb have the minimum for a certain roll rotation speed and decrease with decreasing initial roll gap. The effect of melt flow rate on the structure has not been detected under the adopted experimental conditions.
Regarding the relationship between the solidification structure and the cooling rate of melt, a preliminary experiment of the rapid quenching from melt has revealed that with increasing cooling rate the structure consisting of Sb phase becomes globular and the average size decreases.
Furthermore, velocity and temperature fields of the process were estimated using a mathematical model to discuss effects of key process parameters on cooling rates of the rapidly solidified metallic ribbons. The estimated results show that under the adopted experimental conditions the mean cooling rate in the melt region between rolls has a maximum for a certain roll rotation speed and increases with decreasing initial roll gap. These theoretical predictions qualitatively agree with results obtained from the observed solidification structure.