Effect of Temperature on the Mechanical Properties and Deformation Mechanism of a High Mn Steel With Composite Structure

Abstract

A composite high manganese structure comprising recovered and recrystallized structures was prepared using a single-phase austenitic Fe-30Mn-0.14C-7Cr-0.26Ni steel by cold rolling and annealing. The yield strength and elongation of the composite increased simultaneously, when the tensile temperature decreased from room temperature (RT) to low temperature (−180 • C). The composite structure exhibited a good combination of strength and ductility at RT and −180 • C. The notable mechanical properties at low temperature can be attributed to the enhanced strain-hardening capability via introducing multiple deformation mechanisms in the composite structure.

Microstructure Evolution and Tensile Properties of Cold-Rolled and Annealed Fe-30Mn-0.14C-7Cr-0.26Ni Steel

“…According to Table 3, the stacking-fault energy of all samples with different grain size was within the range that can induce the production of deformation twins. Our previous study confirmed that deformation twins are produced in ultra-fine-grained experimental steel under tensile deformation [34]. Fig.…”

“…Thus, Cr 23 C 6 can promote deformation-induced martensite transformation during the deformation process [40]. However, according to the results of our previous study [34], in both the fine-or coarse-grained samples, no martensite was produced after tensile fracture.…”

“…This was followed by annealing at 600, 700, 800, and 900 o C for 1 h to obtain a laminated composite structure composed of recovered and recrystallized layers and fully recrystallized grains. The structure of the cold-rolled plate was a fully austenitic structure, which has also been reported in the literature [34]. Samples with different microstructure were obtained by 95% cold rolling followed by annealing at 600 900 C for 1 h. Uniaxial tensile tests with the tensile direction aligned along the rolling direction were performed using an MTS tensile testing machine at an initial strain rate of 10 -3 s -1 at room temperature.…”

“…The mean grain size after annealing at 600, 700, 800, and 900 C for 1 h was 0.65, 0.80, 1.07, and 5.75 µm, 13 respectively. Since the samples annealed at 900 C experience no precipitation strengthening and dislocation strengthening, the Hall-Petch relationship of coarse-grained structures used in our previous study was employed to calculate the grain boundary strengthening [34].…”

“…The improved corrosion resistance can overcome the limitations that prevent the application of such alloys in certain environments. Moreover, the addition of Ni can improve the toughness of the alloy and reduce its ductile brittle transition temperature, thus improving its mechanical properties at low temperature [33,34].…”