A new combinatorial processing route to achieve an ultrafine-grained, multiphase microstructure in a medium Mn steel

Heterogeneous Multiphase Microstructure Formation through Partial Recrystallization of a Warm-Deformed Medium Mn Steel during High-Temperature Partitioning

“…These phase transformations that may occur during isothermal holding can affect the final volume fraction and the chemical stability of RA. The expansions observed here are most probably associated with the austenite decomposition, which has also been investigated in the previous work [ 44 ]. The decomposition processes may reduce the austenite fraction, so that if less new austenite forms, the amount of RA will decrease despite its higher stability.…”

“…The Mn contents at points 1, 2, and 3 were measured to be 6.7%, 2.8%, and 15.7%, respectively. The equilibrium concentrations of Mn in austenite, ferrite, and cementite were calculated to be about 7.34%, 1.46%, and 13.85% at 650 °C, as reported elsewhere [ 44 ]. This suggests that point 1 in Figure 9 c corresponds to the austenitic area, while point 2 is in the ferritic region, and point 3 lies in cementite.…”

“…Though several processing strategies have since been individually investigated for accelerating the partitioning of alloying elements and promoting the heterogeneity in the final microstructure of MMnSs, incorporation of a controlled combination of these strategies, however, might seemingly be more effective in enhancing mechanical properties from the microstructure engineering perspective. In the previous work [ 44 ], a combination of factors accelerating the stabilization of austenite, including pre-existed austenite, pre-deformation at 250 °C, and high-temperature partitioning was employed to create a refined microstructure in a 0.31C-4Mn-2Ni-0.5Al-0.2Mo (in wt.%) steel. In the present work, a modified process is proposed to produce a heterogeneous multiphase microstructure consisting of martensite, recrystallized ferrite, pre-existed austenite, reverted austenite, and carbides by warm deformation at a higher temperature promoting partial recrystallization of ferrite and austenite reversion in an MMnS.…”

Mechanism and Application of Reverse Austenitic Transformation in Medium Mn Steels: A Systematic Review

“…[7] Therefore, the annealing at different temperatures could produce a Mn concentration gradient in reverted austenite. [91][92][93][94][95][96] Several additional annealing processes have been proposed for this purpose, as summarized in Figure 6. When the Mn-lean region of reverted austenite has a higher martensitic transformation start (M s ) temperature than the room temperature, it transforms to martensite during cooling, resulting in the refined mixture of austenite and martensite.…”

“…Several processing strategies for achieving austenite grains with Mn concentration gradients in MMS. The possible microstructures at room temperature (RT) after the processing routes in a) [91] and b) [98][99][100] are shown in c) while those in d) [92,93] and e) [94][95][96] are shown in f ). A1 and A3 temperature are the austenitic transformation start and finish temperatures, respectively.…”