Work Hardening Behavior of Medium Mn TWIP+TRIP Steel with a Bimodal Microstructure

摘要

The work hardening behavior of intercritically annealed 6％ Mn steel with a bimodal microstructure was investigated.After intercritical annealing,the steel contained coarse-grained δ-ferrite and ultrafine-grained ferrite and retained austenite.Ductile ultra-high strength behavior was achieved by the combined activation of the twinning-induced (TWIP) and transformation-induced (TRIP) plasticity-enhancing mechanisms.The composition and stacking fault energy (SFE) of the retained austenite,both of which depend on the intercritical annealing temperature,are the key factors which determine the work hardening behavior of the steel.An excellent strength-ductility balance of approximately 26000～52000 MPa·％ was achieved after intercritical annealing in the 740～880°C temperature range.