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 microstructure of a single phase fcc-based Al5Co15Cr30Fe25Ni25 high entropy alloy is evaluated in this study. As-cast ingots of the high entropy alloy were thermo-mechanically processed following different routes involving forging, cold rolling, warm rolling or hot rolling. In addition, the microstructural evolution of highly deformed cold rolled sheets with the annealing temperature was analyzed. The data reveal that a high-volume fraction of the microstructure commences to recrystallize from 600 degrees C. In the absence of recrystallization, i.e., below 600 degrees C, the hardness of thermo-mechanically processed and annealed samples was very close. When recrystallization takes place, the thermo-mechanically treated alloys exhibit higher hardness than the annealed alloys because the recrystallized grains are strengthened by dislocations generated in further steps of the processing while the alloys in the annealed condition are free of dislocations. Maximum hardening is found for the alloy warm-rolled at 450 degrees C and the alloy cold-rolled plus annealing at 500 degrees C for 1 h. Diffusion of solute atoms to the core of dislocations, pinning its movement, accounts for the additional hardening.

Automated summary

The effect of thermos-mechanical processing and thermal treatments on the microstructure of a single phase fcc-based Al5Co15Cr30Fe25Ni25 high entropy alloy is evaluated. Different routes of thermo-mechanical processing (forging, cold rolling, warm rolling, hot rolling) were followed and the microstructural evolution of highly deformed cold rolled sheets with annealing temperature was analyzed. The results show that recrystallization of the microstructure begins at 600 degrees C, leading to higher hardness in the thermo-mechanically treated alloys compared to the annealed alloys.