Microstructure and Strengthening Mechanisms in Fine-Grained and High-Strength Tungsten Heavy Alloy with a Non-Equiatomic Ni5.5Fe2.5CoCr High-Entropy Binder

Fine-grained tungsten heavy alloys (WHAs) with a non-equiatomic Ni5.5Fe2.5CoCr high entropy alloy (HEA) as binder were successfully fabricated through spark plasma sintering (SPS). The influence of binder content and composition on the microstructure and mechanical properties of WHAs were systematically investigated. The average W grain size and W-W contiguity decreased with increasing Ni5.5Fe2.5CoCr content. The Ni5.5Fe2.5CoCr binder inhibited the growth of tungsten grains, resulting in finer tungsten grains (3.5±1.5 μm) in the 90W-Ni5.5Fe2.5CoCr alloy than in the conventional 90W-7Ni-3Fe alloy. This alloy showed an excellent tensile strength of 1392±33 MPa. The high strength is achieved through the synergistic effect of fine-grain strengthening, twinning strengthening, dispersion strengthening and solid-solution strengthening. In contrast, WHAs using equiatomic NiFeCoCr as binder showed lower tensile strength (540±26 MPa), caused by the formation of brittle μ phase in the binder phase. This work provides a pathway for utilizing the non-equiatomic HEA as a binder in the development of high-strength WHAs, thereby expanding their application prospects.