Phase-Field Modeling of Austenite Formation from a Ferrite plus Pearlite Microstructure during Annealing of Cold-Rolled Dual-Phase Steel

摘要

The prediction of microstructure and, consequently, of mechanical properties, as a function of chemical composition and heat treatment parameters, is currently a major topic of scientific investigations. There has been considerable effort to investigate the phase transformation during cooling and its modeling. In comparison, the metallurgical processes of the ferrite-austenite transformation during heating and annealing have not been intensively studied. However, the austenite formation during heating and annealing has a great influence on the final microstructure, as it is one of the first steps in the complex microstructure development of modern high-strength strip steels. In this study, the simulation of austenite formation from a ferrite plus pearlite microstructure during heating is realized by means of a multiphase-field approach. For the description of pearlite dissolution, a simple pseudo-phase approximation is used, which neglects the substitutional elements. Instead, the modeling of austenite formation from ferrite is performed as a second step, taking into account the substitutional elements under LE negligible partitioning (LENP) conditions, using direct coupling to a commercial thermodynamic database. The results of these two-dimensional (2-D) simulations will be presented and compared with experimental findings.