Abstract:Al0.8CoCrFeNiTi0.2 high entropy alloys were prepared by vacuum arc melting and were treated by vacuum annealing at 600 ℃, 800 ℃ and 1000 ℃ for 10h. The microstructure, mechanical properties and corrosion resistance of the as-cast and annealed alloys were studied using XRD, OM, EPMA, hardness tester, universal testing machine, and electrochemical workstation. Microstructure analysis shows that the Annealing treatments have changed the phase composition and microstructure morphology of the alloys. The as-cast alloy consists of BCC and FCC solid solutions, while the 600 ℃, 800 ℃ and 1000 ℃ annealed alloys consist of BCC, FCC and σ phase. In the 800 ℃ annealed alloy, the σ phase precipitates the most. During the annealing process, the single-phase solid solution dendrites in the as-cast shift to the thin layer-flake two-phase mixed structure. In the temperature range of 800 ℃ and below, the higher the annealing temperature, the mixed structure is finer and the composition uniformity is better. But the 1000 ℃-annealed alloy has a large block single-phase solid solution precipitation, causing elements segregation to intensify. Hardness and compression tests show that all of the as-cast and three kinds of annealed alloys have high hardness, yield strength, fracture strength and plastic deformation, showing good comprehensive mechanical properties and resistance to temper softening. The 800 ℃-annealed alloy has the highest hardness, yield strength and fracture strength, but the as-cast alloy have the best plasticity. Electrochemical corrosion tests show that the as-cast and three kinds of annealed alloys all have good corrosion resistance in the 3.5wt.% NaCl solution and 0.5 mol/L H2SO4 solution and the corrosion resistance of the 800 ℃-annealed alloy is best.