Simulation of Solidification, Microsegregation, and Heat Treatment of Cr-Based Fe–xMn–7.5Al–1.0C Lightweight Steels

In this study, we simulated the solidification behavior, microsegregation, and heat treatment in Fe–xMn–7.5Al–5Cr–1.0C lightweight steels using the CALculation of PHAse Diagrams method. The solidification paths and microsegregation of these steels were calculated with the Scheil-Gulliver model and equilibrium calculator in the Thermo-Calc® software. At the same time, thermodynamic calculations predicted heat-treatment temperatures for different steels. The transformation path of the Fe–xMn–7.5Al–5Cr–1.0C (x = 18 and 20 wt.%) lightweight steels is as following: liquid → liquid + δ-ferrite → δ-ferrite + γ-austenite → γ-austenite → γ-austenite + M7C3, according to equilibrium and Scheil’s calculations. In case of 25 wt.% Mn steel, the two-phase region of δ-ferrite and γ-austenite is absent in the transition path. The segregation behaviour of solute elements in the liquid, ferrite, and austenite phases were predicted using the Scheil model. The heat treatment temperature for single-phase formation is expected to be between 900 °C and 1030 °C.