Extended strain hardening by a sequential operation of twinning induced plasticity and transformation induced plasticity in a low Ni duplex stainless steel

Extended strain hardening was realized by a sequential operation of twinning induced plasticity (TWIP) followed by transformation induced plasticity (TRIP) in a Fe-20Cr-3Mn-2Cu-1Ni-1Si-0.2N duplex stainless steel (DSS). As a result, the present DSS exhibited an excellent combination of strength — ductility of 900 MPa which was 75% superior to that of conventional DSSs. The deformed microstructures of the present DSS revealed that strain induced martensite (SIM) causing TRIP primarily nucleated at intersections of mechanical twins without formation of ε martensite which is an intermediate phase during SIM transformation. In addition, the sequential operation of TWIP-TRIP enables strain hardening to be extended to higher strains compared to the operation of TWIP alone.