On the Formability of Medium Mn Steel Treated with Varied Thermal Processing Routes

Abstract

In this contribution, we investigate the influence of thermal processing routes on the formability of medium Mn steel by assessing the strain hardening coefficient and anisotropy factor using the uniaxial tensile test. Medium Mn steel processed by intercritical annealing (IA) at 680 °C for 4 h demonstrates better formability than steel treated with a combination of IA at 800 °C for 10 min and quenching and partitioning (Q&P), based on the much higher strain hardening coefficient (n) and comparable anisotropy factor (r, rm, ∆r). The higher strain hardening coefficient of medium Mn steel with single IA treatment is ascribed to the enhanced transformation-induced plasticity (TRIP) effect resulting from the large amount of austenite that is transformed into martensite during deformation. In addition, the IA process allows for the production of medium Mn steel with high ductility, which is beneficial for its high formability and good ‘part ductility’ in lightweight automotive applications.

Effect of the intercritical annealing in the formability and microstructure of a medium Mn steel sheet

“…Yi et al [4] have mentioned that the actual trend for developing AHSS that exhibit more than 30% of total elongation is with the purpose to ensure a successful plastic forming and also maintain enough "residual ductility" in the part for a crash event. Recently, Zhang et al [5] reported the effect of different heat treatments on the formability of a Fe-10Mn-0.2C-2Al-0.1V (in wt.%) steel. They concluded that IA produced better formability in terms of strain hardening in comparison with the IA-Q&P treatment, it was associated to an enhanced TRIP effect produced in the first treatment.…”