Effects of Applied Stress on Isothermal Phase Transformation of Austenite to Pearlite in Heavy Rail Steels: An Experimental and Modeling Study

摘要

Recently, high-speed train systems are developing rapidly throughout the world. The heavy rail steel for the high-speed train needs to be heat treated after hot rolling, in order to improve its mechanical performances and to meet engineering requirements. This study aims at effects of applied stress on isothermal phase transformation of austenite to pearlite in heavy rail steels during heat treatment. Transformation kinetics and transformation plasticity models for isothermal phase transformations in the heavy rail steel have been established. The effects of stress on transformation kinetics and transformation plasticity have been analyzed. Also, the effects of stress on the morphology of the generated pearlite microstructure have been observed by confocal laser scanning microscopy and scanning electron microscopy. The results show that stress can speed up the transformation of austenite to pearlite. And, with increasing stress, the interlamellar spacing of lamellar pearlite decreases and the fraction of globular pearlite (exhibiting very short, globular-shaped lamellae) increases.