Deformation behavior in cold-rolled medium-manganese TRIP steel and effect of pre-strain on the Luders bands

Deformation behavior was studied in cold-rolled 0.2C-1.6Al-6.1Mn-Fe transformation-induced plasticity (TRIP) steel subjected to intercritical annealing. The steel intercritically hardened at 650 degrees C exhibited excellent mechanical properties, and the excellent ductility was primarily associated with the discontinuous TRIP effect. Moreover at 650 degrees C, the formation of Luders bands was associated with TRIP effect and cooperative dislocation glide. The length of Luders strain was gradually reduced with increasing pre-strain, and was eventually eliminated when the pre-strain was increased to 10%. The increased average stability of retained austenite and increased dislocation density in ferrite induced by pre-strain was responsible for decrease and ultimate elimination of Luders bands. While in steel intercritically annealed at 600 degrees C, ferrite and austenite was predominantly deformed, which was responsible for poor work hardening rate and inferior tensile properties.