Martensite–austenite transformation kinetics of high Cr ferritic heat-resistant steel

Abstract

Abstract The isochronal transformation behavior from martensite (α′) to austenite (γ) of modified high Cr ferritic heat-resistant steel was analyzed using the kinetic information extracted from differential thermal analysis results. The thus obtained α′→γ transformation kinetic process has been described by a JMAK-like model including three overlapping processes: site saturation nucleation, diffusion-controlled growth, and impingement correction for random distribution of nuclei. It is found that both the diffusion of alloying components and the inhibition of carbide precipitates strongly affect the α′→γ transformation kinetic processes. The α′→γ transformation (at relatively low heating rates) is of diffusion-controlled nature, and the obstruction of carbides during the migration of the α′/γ interface leads to a decrease in the pre-exponential factor of diffusion coefficient.