Study of the decomposition behavior of retained austenite and the partitioning of alloying elements during tempering in CMnSiAl TRIP steels

Abstract

Tempering approach is designed for better understanding the effects of heat treatment induced by production process when manufacturing on the transformation-induced plasticity steels containing 1.0 wt.% Al. Specific attention is placed on the roles of tempering temperature and the holding time on the decomposition of retained austenite and the redistribution of alloying elements. Using transmission electron microscopy, we found the retained austenite was decomposed into c-carbide and ferrite in the steels tempered at 300 degrees C for 9 h. An increase in the temperature of 400 degrees C and the holding time over 3 h accelerate the nucleation kinetics of cementite formation, leading to the deteriorated thermal stability of austenite. In addition, atom probe tomography studies confirmed the partitioning tendency of alloying elements across the ferrite/cementite interfaces as well as the compositional spikes of Mn at the interfaces during tempering over 400 degrees C for 9 h. (C) 2015 Elsevier Ltd. All rights reserved.