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Free keywords:
Cobalt alloys; Economic and social effects; Entropy; Grain boundaries; Precipitation (chemical); Recrystallization (metallurgy); Ternary alloys, Atomic scale; Fault planes; Medium entropy; Nucleation sites; Partial recrystallization; Recrystallisation; Recrystallized grains; Sigma-phase precipitation, Chromium alloys
Abstract:
In this work, we discussed the atomic-scale mass transport occurring in a Mo-doped NiCoCr medium-entropy alloy to form σ-precipitates during partial recrystallization at 700°C. We reveal the segregation of Cr/Mo to the fault planes of nano-twins/stacking faults in non-recrystallized zones. Upon annealing, the migration of recrystallized grain boundaries (GBs) redistributes the structure and composition, leading to the annihilation of faults and leaving behind the Mo-rich σ-precursors for precipitation. The segregated Cr/Mo solutes can also diffuse to the moving GBs and create additional σ-nucleation sites. The present results highlight the role of Mo in overcoming strength-ductility trade-off of the alloy. © 2020
