Bainite Formation Kinetics During Isothermal Holding in Modified High Cr Ferritic Steel

摘要

Microstructural observation and high-resolution dilatometry has been employed to investigate the course of isothermal holding at various temperatures during cooling after austenization in a modified high Cr ferritic steel. The formation of bainite during isothermal holding was identified. The amount of bainite increases as transformation temperature decreases. The phenomenon of thermal stabilization of austenite disappears after isothermal holding due to the formation of bainite. The kinetics of incomplete bainite transformation was described by a displacive model in view of autocatalytic nucleation. Kinetics analysis suggests that reduction of holding temperature promotes to bainite transformation by means of an increase in the number of embryos for autocatalytic nucleation and a decrease in activation energy.