1995 年 35 巻 6 号 p. 624-628
The effects of cooling rate on the growth behavior of austenite phase during cooling of an iron-carbon alloy are investigated by means of a numerical simulation . In the cooling process of this alloy, austenite phase nucleates at the interface between δ-ferrite and liquid phases at the peritectic temperature 1768 K and then keeps growing during cooling. The growth mechanisms of austenite phase during cooling are: (1) carbon diffusion from liquid phase through austenite phase into δ-ferrite phase, (2) precipitation from δ-ferrite phase, and (3) crystallization from liquid phase. All these mechanisms induce the growth of austenite phase with increasing cooling rate. The ratio of austenite phase which grows by precipitation and crystallization increases with increasing cooling rate, while that by carbon diffusion decreases. The decrease in the ratio of the diffusional growth is more remarkable for the migration of austenite/liquid interface than for that of δ-ferrite/austenite interface.
