A study of deformation and phase transformation coupling for TRIP-assisted steels

Abstract

A constitutive model for transformation induced plasticity (TRIP)-assisted steels is proposed that considers the elastic-plastic deformation of ferrite and austenite, the austenite-martensite phase transformation and the elastic deformation of martensite. Within this model, an explicit relation between martensite nucleation and plastic deformation within an austenite grain has been established based on the inverse Nishiyama-Wassermann relationship. In particular, strain-induced martensite nucleation and stress-assisted martensite growth have been included in one model with the help of a thermodynamic principle. Furthermore, the formulation of the stress-assisted martensite growth has been enhanced to include commonly observed physical mechanisms infl uencing the martensite transformation and global mechanical behavior of low alloyed TRIP-assisted steels. With this model, we found consistently with experiment that the TRIP effect enhances the effective work hardening rate and hence is benefi cial for improving strength and ductility of steels. The mechanical anisotropy produced by stress-assisted and strain-induced phase transformations are signifi cantly different. We observed that austenite grains transform to martensite more quickly under tension than under compression. Furthermore, the infl uence of alloy composition, martensite lamellar structure, transformation rate and active transformation systems on the strength and ductility of low alloyed TRIP-assisted steels has been investigated. We fi nd that this refi ned model reliably captures the infl uence of alloy composition, temperature, and martensite lamellar structure. It is shown that the choice of the orientation relationship between austenite and the martensite does not signifi cantly infl uence the global mechanical behavior of TRIP-assisted steel.

Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

“…Previous researches related this enhanced work hardening capacity to several factors such as deformation twins, ε-martensite, the formation of stacking faults, low SFE and the consequent slip planarity, and most importantly to the α′-martensite transformation [64,65]. The DIMT is associated with a strong increase in the work-hardening rate with the consequence of increasing the tensile strength.…”

Shot peening of TRIP780 steel: Experimental analysis and numerical simulation

“…They have shown that the crystallographic texture and the elastoplastic properties of ferrite have a strong effect on the transformation kinetics and on the mechanical behavior. Ma and Hartmaier (2015) have implemented in Abaqus, a finite transformation crystal plasticity and variant selection model based on thermodynamic principles to model the behavior of TRIP assisted steel. With a finite element representation, they have explicitly modeled the microstructure with austenitic grains embedded in a ferritic matrix.…”

Microstructural Influences on Fracture at Prior Austenite Grain Boundaries in Dual-Phase Steels

“…The competing kinetics can also be captured using gradient flow models of the Ginzburg–Landau type. Most of the modeling tools are, however, not fully developed for the problem at hand and do not account for all possible nucleating variants corresponding to an orientation relation scheme, with the exception of [22]. Within this restriction, the knowledge of transformation strains associated with individual variants can still be used to extend the understanding gained in the previous section.…”