Microstructure-based constitutive modelling of low alloy multiphase TRIP steels

Abstract

The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP)steels consists of ferrite, bainite, and metastable retained austenite, which can be transformed intomartensite by plastic deformation. In some cases, residual martensite can be present in the initialmicrostructure. The mechanical behavior of these steels depends on the interaction between theintrinsic characteristics of the existing phases and the austenite stability. Due to these factors,the definition of their true stress-strain flow law is complex. This work presents the mechanicalcharacterization of a phenomenological constitutive stress-strain flow law based on the Bouquerelet al. model, as evaluated for three TRIP steels of the same composition but undergoing different heattreatments. Morphological aspects of the existing phases, austenite stability, and suitable mixturelaws between phases are considered. The model is found to accurately reproduce a true stress-strainflow law obtained under tensile uniaxial conditions and provide detailed information on the effectivestress strain partition between the existing phases.