The effect of strain-induced martensitic transformation (SIMT) on the heterogeneous deformation behavior among constituent phases in TRIP-assisted duplex stainless steel

Abstract

Transformation-induced plasticity (TRIP) assisted duplex stainless steels (DSSs) possess a multi-phase microstructure during tensile deformation due to strain-induced martensitic transformation (SIMT). The characteristics of martensitic nucleation in the metastable austenite phase were characterized using the EBSD-based in-situ tensile test and crystal plasticity finite element method (CPFEM). In particular, the nucleation-controlled SIMT kinetic criteria involving nucleation at the intersection or/and boundary of fault-bands was integrated into the crystal plasticity model based on the determination of SIMT initiation in the in-situ tensile test. The accuracy of the model is verified by the evolution law of the volume fraction of martensite and the characteristics of phase transition positions. The initial nucleated martensite pinned austenite to develop the SIMT rapidly. With further deformation, the martensite gradually intersects with each other, forming a package to encapsulate the austenite, hindering the deformation of the austenite to inhibit the SIMT. The martensitic transformation inhibits the occurrence of local strain concentration, and the increase of volume fraction of martensite leads to a decrease in the coefficient of variation about strain distribution in the austenite+martensite system, indicating a more coordinated deformation of the austenite+martensite system. With a further transformation of martensite, the partition strain of the ferrite increases, and the deformation incongruity increases between the ferrite and the austenite+martensite system.