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Cold unidirectional/cross‑rolling of austenitic stainless steels: a review

Mohammadzehi Sara, Mirzadeh Hamed

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 3

art. no. e129

The effects of cold unidirectional/cross-rolling on the development of substructure, strain-induced martensitic transformation, crystallographic texture (preferred orientation), and mechanical properties, as well as the microstructure after subsequent annealing of metastable austenitic stainless steels were overviewed. First, the deformed state was discussed. Compared to unidirectional rolling, it was revealed that cross-rolling leads to the formation of a greater amount of deformation-induced martensite, which is related to the generation of numerous intersecting shear bands and nano-twins, as well as a higher dislocation density in the austenite phase (activation of higher number of slip/twinning systems). It was concluded that these effects are more pronounced at low reductions in thickness. Regarding texture evolution, cross-rolling tends to strengthen the Brass component in the retained austenite phase. Subsequently, the mechanical properties were reviewed, where it was concluded that a more rapid work-hardening and higher strength/hardness at low strains can be obtained due to the effects of cross-rolling on the microstructure. Moreover, while the effects of cross-rolling on the strength at high rolling reductions might not be significant, it is possible to decrease the anisotropy of the sheet due to the alternate change in the rolling direction. Afterward, the annealing of cold-rolled sheets was discussed. It was deduced that cross-rolling might be used for more intense grain refinement based on the thermomechanical processing of cold-rolling and reversion/recrystallization annealing, where the activation of greater number of slip systems, higher dislocation density, and greater martensite content in the deformed state are responsible in this regard. Finally, the suggestions for future works were proposed.

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.