Phase stability and kinetics of σ-phase precipitation in CrMnFeCoNi high-entropy alloys

By G. Laplanche, S. Berglund, C. Reinhart, Aleksander Kostka, F. Fox, Easo P. George. Acta Materialia, 2018

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Abstract Although the phase stability of high-entropy alloys in the Cr-Mn-Fe-Co-Ni system has received considerable attention recently, knowledge of their thermodynamic equilibrium states and precipitation kinetics during high-temperature exposure is limited. In the present study, an off-equiatomic Cr26Mn20Fe20Co20Ni14 high-entropy alloy was solutionized and isothermally aged at temperatures between 600 °C and 1000 °C for times to 1000 h. In the original single-phase fcc matrix, an intermetallic σ phase was found to form at all investigated temperatures. Its morphology and composition were determined and the precipitation kinetics analyzed using the Johnson-Mehl-Avrami-Kolmogorov equation and an Arrhenius type law. From these analyses, a time-temperature-transformation diagram (TTT diagram) is constructed for this off-equiatomic alloy. We combine our findings with theories of precipitation kinetics developed for traditional polycrystalline fcc alloys to calculate a TTT diagram for the equiatomic CrMnFeCoNi HEA. The results of our investigation may serve as a guide to predict precipitation kinetics in other complex alloys in the Cr-Mn-Fe-Co-Ni system.

Subfields: Aerospace Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/955df5e555c748132b7dcca4f09d1bd964781fc2