Comparative Study of the Influence of Reversion‐ and Recovery‐ Annealing on the Mechanical Behavior of High‐Manganese Steels with Varying Stacking Fault Energy

Abstract

High‐manganese steels are promising candidates for application in crash‐relevant automobile components due to their outstanding mechanical properties. These properties result from the activation of additional plasticity effects, such as transformation‐induced plasticity (TRIP) and twinning‐induced plasticity (TWIP). In the present study, we investigate the influence of thermomechanical treatment, specifically by reversion‐annealing, on the mechanical properties. Three alloys with varying stacking fault energy (SFE) values are used: a X8Mn23 TRIP steel (SFE≈5 mJ m−2), a X30Mn22 TWIP/TRIP steel (SFE≈16.3 mJ m−2), and a X30MnAl22‐1 TWIP steel (SFE≈25 mJ m−2). The objective of the study is to combine the beneficial influences of the TWIP and TRIP effect to tailor the mechanical properties. Bimodal microstructures are generated by pre‐deformation with subsequent reversion‐ or recovery‐annealing to correlate the influence of the different microstructural features with the tensile behavior. During reversion‐annealing at 350 °C for 2 min, the previously introduced ϵ‐martensite is transformed to soft austenite. At the same time, dislocations and deformation‐induced twin boundaries are thermally stable. Recovery‐annealing at 550 °C for 30 min results in the annihilation of dislocations, but retention of deformation twins. These bimodal microstructures, comprised of strong and soft austenite, facilitate an improved yield strength‐ductility combination. Reversion‐annealing of the TWIP/TRIP steel results in a slightly higher yield strength with lower total elongation, but decreased work‐hardening rates compare to the recovery‐annealed TWIP steel.