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 into martensite by plastic deformation. In some cases, residual martensite can be present in the initial microstructure. The mechanical behavior of these steels depends on the interaction between the intrinsic 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 mechanical characterization of a phenomenological constitutive stress-strain flow law based on the Bouquerel et al. model, as evaluated for three TRIP steels of the same composition but undergoing different heat treatments. Morphological aspects of the existing phases, austenite stability, and suitable mixture laws between phases are considered. The model is found to accurately reproduce a true stress-strain flow law obtained under tensile uniaxial conditions and provide detailed information on the effective stress strain partition between the existing phases.

Characteristics of advanced high-strength steels obtained by the compact strip production route

“…Figure 5 shows that fitting the data to power relationship, Equation (1), does only agree within a short strain domain, whereas that to exponential type (2) agrees over the yielding to UTS straining domain. Moreover, Equation (2) has been justified in terms of the changes that take over dislocation arrangement as a result of the equilibrium between the dislocations being created to sustain the plastic deformation and their annihilation by restoration mechanisms [38][39][40] and has been used in analyses of plastic deformation in complex multiphase steels [41][42][43]. Use of power type of equation (1) has been criticised by their limitations in covering the full range of plastic strain and that they predict infinite strength [44].…”

Effect of Carbon Content and Intercritical Annealing on Microstructure and Mechanical Tensile Properties in FeCMnSiCr TRIP-Assisted Steels

“…Based on this idea, steels were first developed with a chemical composition (0.15-0.4) wt.% C-(1.5-2.5) wt.% Si-(1.5-2.5) wt.% Mn, which have a polygonal ferrite matrix, achieved by intercritical annealing, and an abundant amount of carbide-free bainitic ferrite plus retained austenite and a minor amount of residual martensite, achieved with bainitic isothermal treatment. Thus, for example, it is known that the plastic forming properties are determined by the characteristics of the retained austenite [10,11]. The named TRIP polygonal ferrite or TPF steel has attained extremely large total elongation up to 30-40% due to the strain induced transformation in a large strain range.…”

Avrami Kinetic-Based Constitutive Relationship for Armco-Type Pure Iron in Hot Deformation

“…To better control and simulate the deforming process, the flow behavior of alloys in hot deformation should be well described. Flow behavior is mainly affected by the deformation temperature, strain rate, strain, inner microstructure and chemical composition [1][2][3]. In previous studies, various constitutive relationships have been constructed to describe the flow behavior during the hot deformation process, which are introduced as follows:…”