The effect of porosity on the austenite to bainite transformation in powder metallurgy steels

摘要

The effect of porosity on the kinetics of the austenite to bainite isothermal transformation in powder metallurgy steels was characterized using a high-speed quenching dilatometer. The measurements revealed that the presence of porosity shortens the incubation time as well as the overall isothermal transformation time. An Avrami-type equation was fitted to the measured data, and the effect of porosity on the nucleation rate of bainite was quantified. In addition, the activation energy for diffusion of carbon atoms during nucleation of bainite was calculated and was found to decrease with increasing porosity.