A comparison of the internal stresses in a transformation-induced plasticity-assisted steel and a twinning-induced plasticity steel

Abstract

An analysis of the loading–unloading behaviour of tensile tests was performed in a transformation-induced plasticity-assisted (TRIP-assisted) steel, duplex high Mn steel (22% Mn–3% Al–3% Si) for a wide range of grain sizes, D. The Bauschinger effect observed during unloading was so strong that plastic deformation was detected before complete unloading was reached. In addition, the yield stress, [Formula: see text], or the flow stress, [Formula: see text], are related to the grain size according to the Hall–Petch relationship. This behaviour was compared with a twinning-induced plasticity (TWIP), steel (22% Mn–0.6% C). The high levels of internal stresses obtained in both steels can be rationalised on account of the reinforcement of the austenitic matrix by the increasing volume fraction of ϵ-martensite or deformation twins of nanometric thickness.

The Influence of the Strain and Stress Gradient in Determining Strain Fatigue Characteristics for Oscillatory Bending

“…None of the cited works have thoroughly analyzed this phenomenon. Although there are theories that consider stress and strain gradients in material fatigue in general, for example, of Gil-Sevillano et al [13], there are none that use it to better predict fatigue life according to the oscillatory bending tests. Therefore, determining the characteristics using tests at different loads for the same materials is required.…”

Effects of temperature and strain rate in strain hardening in torsion of a twinning-induced plasticity steel

“…Consequently, each original grain quickly becomes an aggregate of nanometric parallelepipeds, which represents a dynamic mechanism of Hall-Petch contribution strengthening [12][13][14][15]. In addition to this dynamic mechanism, which contributes as an isotropic hardening, substantial kinematic hardening (giving rise to the Bauschinger-type back stress effect) was involved which accounts for an important part of the flow stress [16][17][18][19][20][21]. Therefore, both mechanisms could be tentatively the origin of the outstanding work hardening rate in these high-Mn steels.…”