Assessment of stress partitioning of a TWIP + TRIP aided lean duplex stainless steel based on the nanoindentation and its application on the twinning evolution

Abstract The evolution of deformation twinning in lean duplex stainless steels (LDSSs) with coupled transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) mechanisms was investigated. Initial large austenite was gradually fragmented into finer units with the development of TRIP/TWIP. The stress-strain relationships of individual phases including austenite, ferrite and strain-induced martensite were validly extracted through inversely determining the micro-constituents' mechanical properties from the nanoindentation load-depth (P-h) curves. Using a rule of mixtures method, the tensile curve of TWIP+TRIP aided LDSS was reasonably predicted. In this context, the stress partitioning behaviors between various constituent phases were further quantified, and the stress contribution of each phase during deformation was clearly characterized. Further, the kinetics law of deformation twinning was modified by especially considering the stress partitioning and the fragmentation of austenite, whereby the effect of TRIP on the TWIP was highlighted.