Dual-phase WNbTaV refractory high-entropy alloy with exceptional strength and hardness fabricated via spark plasma sintering

Refractory high-entropy alloys (RHEAs) show great promise in high-temperature structural and armor-piercing applications. In this study, equal-atomic WNbTaV RHEAs was synthesized using ball milling and spark plasma sintering (SPS). The effects of sintering temperatures on the phase formation, microstructural evolution, and mechanical properties were investigated, and the strengthening mechanisms were also discussed. The results revealed that the milled powders had not yet reached full alloying, where complete alloying can be achieved by further sintering. WNbTaV RHEA samples sintered at temperatures ranging from 1300 degrees C to 1600 degrees C comprised two phases: W(Ta)-rich (BCC1) and Nb(V)-rich (BCC2). Fine and non-preferentially oriented microstructures were obtained, with average grain sizes of 0.97 mu m at 1300 degrees C, 1.08 mu m at 1400 degrees C, 1.12 mu m at 1500 degrees C, and 3.64 mu m at 1600 degrees C. The RHEAs sintered at 1300 degrees C to 1500 degrees C exhibited both intergranular and transgranular fractures, while the sample sintered at 1600 degrees C displayed only transgranular fractures. Notably, the RHEA sintered at 1500 degrees C exhibited an impressive combination of yield strength (2910 MPa) and hardness (9.06 GPa). The extraordinary high strength of the WNbTaV RHEAs was predominantly attributed to the synergistic effects of fine grain strengthening, solid solution strengthening, and dislocation strengthening. The calculated contributions underscore that the sintering temperature plays a crucial role in optimizing the mechanical properties of the WNbTaV RHEA through the interplay of various strengthening mechanisms.