Heterogeneous microstructural design with a bimodal grain size distribution of a multicomponent alloy by reversion from a strain-induced martensite

초록

The aim of this study was to design a simple thermo-mechanical process for multicomponent alloys by fabrication of bimodal-grained distribution, to improve the strength level without a significant strength-ductility trade-off. The corresponding process used reversion from strain-induced body-centered-cubic (BCC) to face-centered-cubic (FCC). The V10Cr10Fe45Co35 alloy exhibited two-phase microstructure of strain-induced BCC and deformed FCC phases after cold rolling. During reversion annealing, the strain-induced BCC phase reverted to ultrafine FCC grains because the martensitic substructure provided ample nucleation sites, while the deformed FCC grains were recrystallized and grown to relatively coarse grains, leading to a bimodal-grained distribution. The annealing temperature was selected as the temperature immediately above the reversion finish temperature. The corresponding alloy exhibited an excellent combination of strength and ductility over 45,000 MPa % and showed yield strength (nearly 1 GPa) two to three times higher than those of conventional FCC-based multicomponent alloys. This was most likely due to the bimodal-grained distribution and active transformation-induced plasticity in metastable ultrafine FCC grains. © 2023 Elsevier B.V.

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