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

Journal Article · Sat Dec 01 00:00:00 EST 2018 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2018.09.040· OSTI ID:1474747

Laplanche, G. ; Berglund, S.; Reinhart, C.; Kostka, A.; Fox, F.; George, E. P.

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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ruhr Univ., Bochum (Germany)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); German Research Foundation (DFG)
• Grant/Contract Number: AC05-00OR22725; LA 3607/1-1; GE 2736/1-1
• OSTI ID: 1474747
• Alternate ID(s): OSTI ID: 1479735
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Vol. 161 Journal Issue: C; ISSN 1359-6454
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
high entropy alloys
CoCrFeMnNi
microstructure
TTT diagram
Johnson–Mehl–Avrami (JMA) equation