Abstract
In this paper, the effects of the deformation temperature, the deformation reduction and the deformation rate on the microstructural formation, ferritic and martensitic phase transformation, stress–strain behaviors and micro-hardness in low-carbon ferritic stainless steel were investigated. The increase in deformation temperature promotes the formation of the fine equiaxed dynamic strain-induced transformation ferrite and suppresses the martensitic transformation. The higher deformation temperature results in a lower starting temperature for martensitic transformation. The increase in deformation can effectively promote the transformation of DSIT ferrite, and decrease the martensitic transformation rate, which is caused by the work hardening effect on the metastable austenite. The increase in the deformation rate leads to an increase in the ferrite fraction, because a high density of dislocation remains that can provide sufficient nucleation sites for ferrite transformation. The slow deformation rate results in dynamic recovery according to the stress–strain curve.
Highlights
Ferritic stainless steels have been widely used in railway transportation equipment, mining machinery, the auto industry and nuclear fission power plant components, because of their remarkable corrosion resistance, outstanding strength and toughness, good weld ability and high cost performance [1,2,3,4,5]
Severe plastic deformation is a practical route for the improvement of mechanical properties in the ferritic stainless steels, since in their case it is difficult to realize the effect of phase transformation strengthening [10]
It has been recognized that ultrafine grain structure can be obtained during severe plastic deformation in ferritic stainless steels [11]
Summary
Ferritic stainless steels have been widely used in railway transportation equipment, mining machinery, the auto industry and nuclear fission power plant components, because of their remarkable corrosion resistance, outstanding strength and toughness, good weld ability and high cost performance [1,2,3,4,5]. The dynamic recrystallization may occur in the coarse-grained structure during severe plastic deformation at ambient temperature [13] Due to their restricted ferrite-forming elements, low-carbon ferritic stainless steels may enter the austenite phase regions at high temperature. The effect of austenitic transformation and the subsequent decomposing of austenite on severe plastic deformation in low-carbon ferritic stainless steels should be considered, though it has been rarely reported until now. Metals 2019, 9, 463 subsequent decomposing of austenite on severe plastic deformation in low-carbon ferritic stainless steels should be considered, though it has been rarely reported until now. This project focuses on the high temperature plastic deformation in the austenite phase region.
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