The effects of external compressive stress on the kinetics of low temperature bainitic transformation and microstructure in a superbainite steel

Abstract

Abstract The effects of external compressive stress below the yield strength of austenite on the kinetics of low temperature bainitic transformation and microstructure in a superbainite steel were studied through dilatometry, scanning electron microscopy and X-ray diffraction analysis simultaneously. The results show that even under a relatively low isothermal temperature of 300°C, compressive stress less than yield stress can clearly accelerate bainitic transformation because of the increase in total driving force for bainitic transformation and anisotropic transformation strain. Bainite ferrite becomes longer, the orientations of bainite sheaves become more uniform and the transformation strain becomes anisotropic under external compressive stress because of variants selection. The amount of bainite increases while the amount of martensite decreases with the application of external stress.