Abstract
Intergranular proeutectoid ferrite nucleation in a V-N steel has been examined at isothermal transformation at 600°C with respect to the austenitizing temperatures. While substantial grain growth takes place, the number of intergranular ferrite grains per unit grain boundary area decreases with increasing austenitizing temperatures. Non-stationary increasing rate with time is observed. Overall transformation during isothermal transformation delays after austenitizing at higher temperatures and follows the Johnson-Mehl-Avrami formula for the case of fast grain boundary nucleation. It is discussed that the decrease in the intergranular ferrite nucleation rate associated with higher austenitizing temperatures is partially due to grain boundary structures, not merely to the decrease in the nucleation sites associated with grain growth. Use of high austenitizing temperature is requisite for the intragranular ferrite precipitation.
