Understanding martensite and twin formation in austenitic steels: A model describing TRIP and TWIP effects

Abstract

A unified description for the evolution of-and α-martensite, and twinning in austenitic steels is presented. The formation of micron-scale and twin bands is obtained by considering the evolution of hierarchically arranged nano-sized and twins (embryos). The critical size and applied stress when these structures form is obtained by minimising their free energy of formation. The difference between forming an plate or a twin lies in the number of overlapping stacking faults in their structure. A nucleation rate criterion is proposed in terms of the critical embryo size, resolved shear stress and embryo number density. Based on Olson and Cohen's classical α-martensite transformation model, the nucleation rate of α is considered proportional to that for. These results, combined with dislocation-based approximations, are employed to prescribe the microstructure and flow stress response in steels where transformation-induced-plasticity (TRIP) and/or twinning-inducedplasticity (TWIP) effects operate; these include austenitic stainless and high-Mn steels. Maps showing the operation range of , α and twinning in terms of the stacking fault energy at different strain levels are defined. Effects of chemical composition in the microstructure and mechanical response in stainless steels are also explored. These results allow identifying potential compositional scenarios when the TRIP and/or TWIP effects are promoted in austenitic steels.

Effect of Deformation Temperature on Microstructure Evolution and Mechanical Properties of Low‐Carbon High‐Mn Steel

“…Among new steel grades developed for application to car bodies [1][2][3][4][5], high-manganese austenitic steels are attractive materials for the automotive industry because of their unique combination of high strength, ductility, and formability. High-manganese steels are characterized by a high work-hardening rate resulting from TRIP (transformationinduced plasticity), TWIP (twinning-induced plasticity), or SIP (shear-induced plasticity) effects [6,7].…”

Design of a high strength, high ductility 12 wt% Mn medium manganese steel with hierarchical deformation behaviour

“…Several factors could be at work. The SFE calculation may be erroneous as the empirical model [27] used in this study was not developed for use in medium Mn steel but more importantly, the deformation mode in medium Mn steels cannot be determined by SFE alone, unlike TWIP steels which do not transform [41]. In this scenario, the austenite stability of the core austenite grains was such that strain induced martensitic transformation was preferable to twinning.…”

Microstructural Evolution and Strain-Hardening in TWIP Ti Alloys

“…where d ρ/ d dis represents the evolution of dislocation density in the untwined β-matrix. It results from the competition between dislocation accumulation d ρ + /d dis and annihilation d ρ − /d dis due to dynamic recovery [19] . The dislocation storage term incorporates contributions from (i) the dislocation forest induced by dislocation interactions; (ii) the dislocation impedance by grain boundaries; and (iii) the dynamically decreased intertwin spacing L ( Fig.…”

“…Later the effect of backstress was introduced as dislocation pile-up contributes kinematic hardening [18] . Recently, Galindo-Nava and Rivera-Díaz-del-Castillo [19] reported a dislocation-based model particularly considering the nucleation and growth mechanisms of {112} 111 twins and TRIP (transformation-induced plasticity) effect in austenitic steels. The operation range of deformation twinning and martensitic transformation in different strain levels was related to stacking fault energy.…”