A dislocation-attraction model for the first stage of tempering

Abstract

A dislocation-attraction model governing the flow of carbon atoms is proposed to account for the kinetics of the first stage of tempering in steel. It is predicted that the time exponent of the isothermal reaction should be 1 3 , and the activation energy for the reaction should equal that for diffusion of carbon in martensite. On the basis of previous kinetic data, a good check of the theoretical time exponent is obtained; however, it appears that the activation energy for diffusion of carbon is about 50% higher in martensite than in α-ferrite. The slower rate of carbon diffusion in martensite is explained by the availability of paths of lower barrier energy in the b.c.c. ferrite than in the b.c.t. martensite.