Quantitatively assessing the contributions of temperature-dependent deformation-induced martensitic transformation to uniform elongation and work hardening of TRIP-assisted duplex stainless steel via crystal plasticity

Abstract

The martensitic transformation produced by transformation-induced plasticity (TRIP) assisted duplex stainless steels (TDSSs) can significantly enhance plasticity and strength of the material under deformation. At different deformation temperatures, the stability of austenite varies, which further affects the varied kinetics of deformation-induced martensitic transformation (DIMT). In the work, The mechanical response during tensile deformation of TDSS in a temperature range of 20 °C–60 °C was investigated. Especially, the quantitative determination of strength- and elongation-contributions of DIMT was characterized by employing crystal plasticity finite element method (CPFEM) considering thermal softening of temperature effect. The higher the temperature is, the weaker the DIMT and resultant TRIP effect are, and hence the contributions of TRIP to work hardening and uniform elongation are correspondingly reduced. The local strain increment is limited after martensitic transformation due to the significant deformation resistance of martensite, and the strain concentration phenomenon has slowed down at martensitic transformation positions. As a result, the maximum value of strain drops, leading to a decrease in the coefficient of variation (CV) of the strain distribution. Providing improvement of the homogeneity of strain, the material exhibits substantial enhanced plasticity characteristics. The global stress increment is lower than the ideal linear law calculated based on stress mixing that the global stress increment is proportional to the volume fraction of martensite. The stress increment caused by martensitic transformation has a certain degree of postponed effect and transformation rate dependence.