Deformation behavior of a high-plasticity nano/ultrafine-grained N-bearing duplex stainless steel: Twin/twin-like induced plasticity effect

The present study deals with the grain refinement of a high nitrogen duplex stainless steel through cold rolling up to 80% and subsequent reversion annealing in the range of 750 degrees C to 1100 degrees C at various duration times. The microstructural observations showed that the nano/ultrafine-grained (NG/UFG) austenite with the grain size of 400 nm was obtained by annealing at 900 degrees C for 30 s due to alpha-martensite to austenite complete reverse transformation. The NG/UFG duplex steel indicated a superior mechanical properties consist of 1 GPa yield strength (YS) and 40% elongation to fracture. The transmission electron microscopy study of the tensile deformed NG/UFG material indicated that the nature of extraordinary plasticity in NG/UFG material is because of the dense planar defects, specifically, the twin/twin-like induced plasticity effect in austenite, accompanied with strain accommodation of coarse grain ferrite phase.