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Tailoring the strength-ductility balance of a commercial austenitic stainless steel with combined TWIP and TRIP effects

Sohrabi Mohammad Javad, Mirzadeh Hamed, Sadeghpour Saeed, Geranmayeh Abdol Reza

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 3

art. no. e170, 2023

The sequential twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) effects were induced in a commercial AISI 304L stainless steel by tailoring the average austenite grain size (via thermomechanical processing of cold rolling and reversion/recrystallization annealing), leading to a combination of high yield stress and total elongation as well as a remarkable strength-ductility synergy similar to advanced high-strength steels (AHSS) for automotive industry. In fact, the refinement of grains promoted the TWIP effect at the expense of the TRIP effect due to its effect on increasing the apparent stacking fault energy; while the coarsening/growth of grains led to a pronounced TRIP effect via deformation-induced martensitic phase transformation during straining. Moreover, the TRIP/TWIP effects were characterized by the simple work-hardening analysis such as slope change and appearance of extremum points on the curves of work-hardening rate, logarithmic and parabolic segments on the curves of instantaneous work-hardening exponent, and deviations from the strain-hardening Hollomon lines. The results were supported by the interrupted tensile tests and detailed electron backscattered diffraction (EBSD) analysis, where the merit of the TWIP-TRIP steels was shown in the case of a commercial austenitic stainless steel.

Deformation-induced martensite in austenitic stainless steels: A review

Sohrabi Mohammad Javad, Naghizadeh Meysam, Mirzadeh Hamed

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

382--405

Recent progress in the understanding of the deformation-induced martensitic transformation, the transformation-induced plasticity (TRIP) effect, and the reversion annealing in the metastable austenitic stainless steels are reviewed in the present work. For this purpose, the introduced methods for the measurement of martensite content are summarized. Moreover, the austenite stability as the key factor for controlling the austenite to martensite transformation is critically discussed. This is realized by analyzing the effects of chemical composition, initial grain size, applied strain, deformation temperature, strain rate, and deformation mode (stress state). For instance, the effect of initial grain size is found to be complicated, especially in the ultrafine grained (UFG) regime. Furthermore, it seems that there is a critical grain size for changing the trend of α′-martensite formation. Decreasing the deformation temperature motivates the formation of α′-martensite, but there is a critical temperature for achieving the maximum tensile ductility. Afterwards, the modeling techniques for the transformation kinetics and the contribution of deformation-induced martensitic transformation to the strengthening of material and also strength-ductility trade-off are critically surveyed. The processing of UFG microstructure during reversion annealing, the effects of the recrystallization of the retained austenite, the martensitic shear and diffusional reversion mechanisms, and the annealing-induced martensitic transformation are also summarized. Accordingly, this overview presents the opportunities that the strain-induced martensitic transformation can offer for controlling the microstructure and mechanical properties of metastable austenitic stainless steels.