Precipitation Hardenable High Entropy Alloy for Tooling Applications

Stryzhyboroda, O. and Hecht, U. and Witusiewicz, V.T. and Laplanche, G. and Asabre, A. and Wilms, M.B. and Weisheit, A.

Volume: 4 Pages: 1427-1433
DOI: 10.1557/adv.2019.146
Published: 2019

We present a high entropy alloy (HEA) from the system Al-Co-Cr-Fe-Ni with small additions of W, Mo, Si and C which was designed to allow for precipitation hardening by annealing in the temperature range from 600 to 900°C. The alloy development was supported by thermodynamic computations using ThermoCalc software and the specimens were produced by arc melting. The microstructure of one selected sample in as-cast and annealed conditions was analysed using SEM/EDS, SEM/EBSD and TEM. The as-cast microstructure consists of spinodally decomposed BCC dendrites enveloped by FCC+Cr 23 C 6 eutectic. Upon annealing at 700°C for 24 h nanoscale precipitates form within the spinodal BCC as well as from FCC. Precipitation is exquisitely uniform leading to an increase in microhardness from 415 HV0.5 in the as-cast state to 560 HV0.5 after annealing. We investigated coarsening of this microstructure using varying holding time for a constant temperature of 700°C. The microstructure evolution during coarsening and the corresponding mechanical properties obtained from instrumented indentation experiments are presented in this work. © Materials Research Society 2019.

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