TWIP effect and plastic instability condition in an Fe-Mn-C austenitic steel

The correlation among deformation twin density, work hardening, and tensile ductility was investigated in an Fe-18Mn-1.2C steel. The twin density was varied by changing tensile deformation temperature from 123 to 523 K. The deformation twin density at a 10% plastic strain decreased with increasing deformation temperature except for the condition (123K) in which martensitic transformation occurred. The work hardening rate at the early deformation stage decreased due to the reduction in the deformation twin density; however, the decrease in work hardening rate did not affect the uniform elongation. The uniform elongation was determined by a plastic instability condition. Thus, the important factor for the uniform elongation is the work hardening rate in the later deformation stage. Additionally, we discussed influences of dynamic strain aging and e-martensitic transformation which accelerated fracture.