Effect of Annealing on Microstructure and Mechanical Properties of Al0.5CoCrFeMoxNi High-Entropy Alloys

The effect of annealing temperature on the microstructure, phase constituents and mechanical properties of Al0.5CoCrFeMoxNi high-entropy complex alloys has been investigated at a fixed annealing time (10 h). The 600 degrees C-annealing has no obvious effect on their microstructures, while the annealing at 800-1200 degrees C enhances the precipitation of (Al,Ni)-rich ordered BCC phase or/and (Cr,Mo)-rich sigma phase, and thereby greatly affects the microstructure and mechanical properties of the alloys. All the annealed Al0.5CoCrFeNi alloys are composed of FCC and (Al,Ni)-rich ordered BCC phases; the phase constituent of the Al0.5CoCrFeMo0.1Ni alloy changes from FCC + BCC (600 degrees C) to FCC + BCC + sigma (800 degrees C) and then to FCC + BCC (1100 degrees C); the phase constituents of the Al0.5CoCrFeMo0.2Ni and Al0.5CoCrFeMo0.3Ni alloys change from FCC + BCC + sigma to FCC + BCC with the annealing temperature rising from 600 to 1200 degrees C; while all the annealed Al0.5CoCrFeMo0.4Ni and Al0.5CoCrFeMo0.5Ni alloys consist of FCC, BCC and sigma phases. The phase constituents of most of the alloys investigated are in good agreement with the calculated results from Thermo-Calc program. The alloys annealed at 800 degrees C under current investigation conditionshave relative fine precipitations and microstructure, and thereby higher hardness and yield stress.