The sequential twinning-transformation induced plasticity effects in a thermomechanically processed high Mn austenitic steel

Abstract

Different initial microstructures with various bimodal grain size distributions (BGSD) were produced in a high Mn austenitic steel through applying a predetermined set of thermomechanical processing cycles. The corresponding room temperature mechanical properties and the related strain hardening behaviors were assessed using tensile testing method. The results indicated that in the microstructure with high grain size bimodality, the length and amplitude of rapid hardening region was well higher than the others. This was attributed to its higher capability to α'-martensite formation. In addition, the threshold strain to initiate martensitic transformation was shifted to the lower one in the microstructure with higher bimodal grain size distribution. The latter was related to the lower arisen back stresses in the interior regions of the coarser grains. Furthermore, different transformation paths were identified as the BGSD changed. The austenite could directly transform to α'-martensite (γ α') in the microstructure with lower BGSD; in this case the α'-martensite mainly appeared at the intersections of deformation twins. In contrast, in microstructures with higher BGSD, the nucleation occurred at the intersections of ε-martensite platelets. The co-existence of these transformation paths provided an extended transformation induced plasticity effect ending to a higher elongation to fracture in the course of deformation. In order to summarize the contribution of various strain hardening mechanisms, a deformation map was also constructed. Accordingly, the enhanced ductility/strength properties were attributed to the sequential operation of extended transformation induced plasticity and twinning induced plasticity effects.

The Correlation of Macrostructure, Microstructure, and Texture with Room Temperature Mechanical Properties of a Twinning‐Induced Plasticity Automotive Steel after Friction Stir Spot Welding/Processing

“…This appears to be reasonable considering the lower mean grain size at this specified condition. In addition, the increase in the bimodality parameter would activate the twipping effect to higher extent, which have been reported by sabzi et al, in the microstructure of the specimen welded at 1600 rpm. Consequently the peak strength of the joints welded at 1600 rpm is higher than that of 1000 rpm.…”

The significance of phase reversion-induced nanograined/ultrafine-grained (NG/UFG) structure on the strain hardening behavior and deformation mechanism in copper-bearing antimicrobial austenitic stainless steel

“…In a recent study, different initial microstructures with various bimodal grain size distributions (BGSD) were obtained in a high Mn austenitic steel (TRIP/TWIP) through rolling at different temperatures [48,49]. The corresponding room temperature mechanical properties and the related strain hardening behavior was assessed via tensile testing.…”

A microscale constitutive model for thin stainless steel sheets considering size effect

“…7 The transformation-induced plastic and twinning-induced plastic effects increase the strain hardening capacity of the austenitic stainless steel sheet metals. 8,9…”

“…7 The transformation-induced plastic and twinning-induced plastic effects increase the strain hardening capacity of the austenitic stainless steel sheet metals. 8,9 In order to manufacture micro components for industrial applications, the understanding of the mechanical behavior of materials is essential to design an appropriate forming process. 10 The traditional knowledge of forming processes established in the macro world could not simply scale down to the micro world because of the size effect phenomenon.…”