Dilatometric Analysis on Phase Transformations of Intercritical Annealing of Fe-Mn-Si and Fe-Mn-Si-Cu Low Carbon TRIP Steels

摘要

Evaluations of austenite fraction and transformation kinetics upon intercritical annealing of low carbon TRIP steels were attempted using quantitative dilatometric analysis. The measured dilatation curves were analyzed by taking the carbon distribution between austenite and its decomposed phases into account. The amount of austenite formed during intercritical annealing and its carbon content obtained by dilatometric measurement was compared with the values predicted by thermodynamic calculations under the ortho-equilibrium and para-equilibrium conditions. The kinetics of the reaustenization process including pearlite dissolution and non-isothermal and isothermal formation of austenite could be quantitatively characterized by means of a modified JMAK (Johnson-Mehl-Avrami-Kolmogrov) equation.