Microstructure evolution during thermomechanical processing in 3Mn-0.1C medium-Mn steel

Abstract

Medium-Mn steels are energetically investigated as a candidate of the third generation advanced high strength steels (AHSSs). However, their phase transformation and microstructaure evolution during various heat treatments and thermomechanical processing are still unclear. The present study first confirmed the kinetics of static phase transformation behaviour in a 3Mn-0.1C medium-Mn steel. Hot compression tests were also carried out to investigate the influence of high-temperature deformation of austenite on subsequent microstructure evolution. It was found that static ferrite transformation was quite slow in this steel, but ferrite transformation was greatly accelerated by the hot deformation in austenite and ferrite two-phase regions. Characteristic dual-phase microstructures composed of martensite and fine-grained ferrite were obtained, which exhibited superior mechanical properties. This paper is part of a Thematic Issue on Medium Manganese Steels.

Effect of Hot Deformation on Phase Transformation Kinetics in Isothermally Annealed 3Mn-1.6Al Steel

“…The increase in the Mn content by 1% significantly slowed the ferritic transformation. These results are confirmed by Hou et al [ 22 ] and Ito et al [ 23 ]. In addition, in the corresponding inter-critical annealing (ferrite (martensite) → austenite, instead of austenite → ferrite) the kinetics of the phase transformation is much faster, as evidenced by many publications, achieving a significant amount of ferrite in a short time [ 37 , 38 ].…”

“…A typical thermo-mechanical processing of medium-Mn steels includes a bainitic step resulting in the producing of bainite-retained austenite mixtures. However, there are only a few studies [ 22 , 23 ] which focus on obtaining austenitic-ferritic microstructures in medium-Mn steels with this method. It requires an isothermal holding at the inter-critical region, instead of bainitic holding during cooling from finish rolling temperature.…”

Enhancing the Mechanical Properties of a Hot Rolled High-Strength Steel Produced by Ultra-Fast Cooling and Q&P Process

“…Along with better formability, the martensite constituents guarantee the strength of the steel and the residual austenite improves the ductility of the steel due to transformation-induced plasticity during the deformation, which is higher than that of the first generation dual-phase (DP) steel [5,6]. In order to further improve the strength of steels and maintain adequate ductility, a quenching-partitioning-tempering (Q-P-T) process was proposed [7,8] for medium manganese steels, though it is characterized by longer processing time and higher cost.…”

Ultrahigh strength-ductile medium-Mn steel auto-parts combining warm stamping and quenching & partitioning

“…Medium Mn steels (3-10 wt-% Mn) have attracted more and more attention for ultra-high strength of over 1 GPa without compromising ductility among a new-generation of advanced high strength steels (AHSSs) [1][2][3][4][5]. These enhanced mechanical properties are mostly due to the coordinated deformation of ultrafine dual or complex phase microstructure and the enhanced transformation-induced plasticity (TRIP) effect resulting from the austenite retained with proper mechanical stability [4,5].…”