Microstructure evolution and mechanical properties of CrFeNi_xV_0.64Ta_0.36 eutectic high-entropy alloys

Eutectic high entropy alloys (EHEAs) have attracted considerable interest because of their excellent casting fluidity and outstanding mechanical properties. In this study, a novel system of EHEAs, namely CrFeNi_xV_0.64Ta_0.36 (1.3 ≤ x ≤ 1.9) was designed and prepared. The microstructure evolution and mechanical properties of CrFeNi_xV_0.64Ta_0.36 EHEAs were investigated in as-cast state. The results showed that the alloy was composed of σ-phase, Fe₇Ta₃-type intermetallic compounds (IMC), and a small amount of the eutectic phase when x = 1.3. A rare bimodal eutectic microstructure [face-centered-cubic (FCC) structure /σ + Fe₇Ta₃-type IMC] was observed in EHEAs, even in high entropy alloys when x = 1.6, 1.7, 1.8, and 1.84. The typical hypo-eutectic microstructure was acquired when x was increased to 1.9. The fully eutectic composition, i.e., CrFeNi_1.85V_0.64Ta_0.36 with alternatingly lamellar FCC and Fe₇Ta₃-type IMC structures exhibited the best mechanical properties, with the compressive yield strength, fracture strength, and engineering strain being 1475.9 MPa, 2799 MPa, and 38.095%, respectively.