Control of the Microstructure in a Al₅Co₁₅Cr₃₀Fe₂₅Ni₂₅ High Entropy Alloy through Thermo-Mechanical and Thermal Treatments

The effect of thermos-mechanical processing and thermal treatments on the microstructureof a single phase fcc-based Al₅Co₁₅Cr₃₀Fe₂₅Ni₂₅ high entropy alloy is evaluated in this study. As-castingots of the high entropy alloy were thermo-mechanically processed following different routesinvolving forging, cold rolling, warm rolling or hot rolling. In addition, the microstructural evolutionof highly deformed cold rolled sheets with the annealing temperature was analyzed. The datareveal that a high-volume fraction of the microstructure commences to recrystallize from 600 C. Inthe absence of recrystallization, i. e. , below 600 C, the hardness of thermo-mechanically processedand annealed samples was very close. When recrystallization takes place, the thermo-mechanicallytreated alloys exhibit higher hardness than the annealed alloys because the recrystallized grains arestrengthened by dislocations generated in further steps of the processing while the alloys in theannealed condition are free of dislocations. Maximum hardening is found for the alloy warm-rolledat 450 C and the alloy cold-rolled plus annealing at 500 C for 1 h. Diffusion of solute atoms to thecore of dislocations, pinning its movement, accounts for the additional hardening.