Microstructures, Mechanical Properties, and Corrosion Behaviors of Refractory High-Entropy ReTaWNbMo Alloys

A refractory ReTaWNbMo high-entropy alloy (HEA) with an equal atomic ratio prepared by rapid solidification displays a BCC crystal structure. After annealing the as-quenched samples at 673, 873, 1073, and 1273 K for 12 h, respectively, the crystalline phase still keeps its BCC structure, but the crystalline morphology transforms from coarse dendrites to fine equiaxed crystals together with gradual grain refinement. The intragranular regions are enriched in W and Ta, while the crystals in the intergranular regions are enriched in Nb, Mo, and Re. With the increase in annealing temperature, the yield strength increases, and the compressive plasticity and fracture strength are obviously enhanced. The failure mode gradually changes from transgranular to intergranular fracture. Furthermore, the corrosion behaviors of the as-cast ReTaWNbMo HEA and the annealed states in a 3.5 wt.% NaCl solution were also studied. The samples annealed at 1273 K exhibit the best corrosion resistance due to the elemental re-distributions within grains.