Exploring hot deformation mechanism and precipitation behavior of Fe–5.6Mn–0.18C–1.1Al(–0.1Ti–0.22Mo) steels through physical modeling and microstructure characterization

Abstract

This study investigated the hot deformation mechanism and precipitation behavior of Fe–5.6Mn–0.18C-1.1Al(–0.1Ti–0.22Mo) steels through hot compression tests conducted at temperatures ranging from 750 °C to 1150 °C and strain rates from 0.01 s−1 to 1 s−1. The flow stress behavior was analyzed using an Arrhenius–type constitutive equation, revealing that Ti–Mo microalloying increased the activation energy for hot deformation by 101.9 kJ/mol. Furthermore, the hot deformation behavior was modeled and predicted using the Bergström model for the work hardening/recovery stage and the Kolmogorov–Johnson–Mehl–Avrami (KJMA) model for dynamic recrystallization (DRX). Microstructural analysis of specimens deformed at 750 °C indicated that deformation–induced ferrite transformation (DIFT) facilitated softening in the intercritical region, with the Kurdjumov–Sachs (K–S) orientation relationship between the deformation–induced ferrite and the parent austenite. At 850 °C, nano–sized (Ti,Mo)C precipitates refined prior austenite grains and suppressed DRX due to a strong pinning effect. However, at 1050 °C and above, precipitate coarsening weakened the pinning effect, resulting in similar flow behavior and microstructural features in both steels.

Keywords

• Medium Mn steel
• Ti–Mo microalloying
• Hot deformation
• Deformation–induced ferrite transformation
• Dynamic recrystallization