Compositional design of CrMnFeCoNi multicomponent alloys based on solid-solution strengthening predictions

This work employed an integrated alloy-design strategy combining theoretical modeling, compositional optimization, and experimental validation, aiming to develop Cr- and Ni-rich multicomponent alloys with enhanced solid solution strengthening. Three quinary alloys (in at%), Cr35Mn5Fe5Co5Ni50 (alloy “A”), Cr42Mn6Fe6Co6Ni40 (alloy “B”), and Cr42Mn5Fe5Co9Ni39 (alloy “C”), were designed using CALPHAD thermodynamic calculations and solid-solution strengthening models to achieve strength levels comparable to those of the ternary, reference alloy, Cr45Co27.5Ni27.5 (alloy “R”), one of the toughest FCC solid solutions known up to date. The compositions were initially designed to form single-phase FCC solid solutions. However, two of the newly developed compositions, namely alloys B and C, exhibited a multiphase microstructure consisting of an FCC matrix with a small fraction of a BCC phase. The theoretical predictions were experimentally validated through microstructural and mechanical characterization, revealing good agreement in the predicted FCC matrix, while the experimentally observed BCC phase in alloys B and C highlighted limitations in predicting phase stability. Consistent with these microstructural differences, the FCC grain sizes varied markedly among the annealed alloys, with average values of 210 ± 96 μm and 90 ± 35 μm for alloys A and R, respectively, while significantly finer grains were obtained for alloys B (7 ± 3 μm) and C (11 ± 4 μm). This microstructural refinement was accompanied by an increase in yield strength, which reached about 430 MPa for alloy B and 410 MPa for alloy C, compared to 240 MPa and 315 MPa for alloys A and R, resulting in a promising combination of microstructural refinement and mechanical strength for alloys B and C. The present results provide new insights into the design of multicomponent alloys within the CrMnFeCoNi system, highlighting the role of composition and processing in controlling their microstructure and mechanical performance.