Microstructure and mechanical properties of tantalum‑hafnium carbide reinforced Ta alloys fabricated by spark plasma sintering

In this paper, two alloys, namely Hf_0.4Ta_0.65(TaC)_0.35 and Re_0.01Hf_0.4Ta_0.65(TaC)_0.35, were successfully prepared by means of mechanical ball milling and spark plasma sintering. The microstructures and mechanical properties of these two alloys were investigated. The results show that the main phase in both alloys is the metallic BCC phase, and the strengthening phases are carbide phases, which are classified as MC-FCC and M₂C-HCP (where M = Hf, Ta). In addition, a small amount of HfO₂ phase is also present in the alloys. The room-temperature yield strength, compressive strength and compressive fracture strain of the Hf_0.4Ta_0.65(TaC)_0.35 alloy are 1350 ± 14.1 MPa, 1627 ± 41.1 MPa and 5.75 ± 0.1 %, respectively. After the addition of Re element, the yield strength, compressive strength and plasticity of the Re_0.01Hf_0.4Ta_0.65(TaC)_0.35 alloy are significantly improved, reaching 1410 ± 39.6 MPa, 1786 ± 8.5 MPa and 6.75 ± 0.9 %, respectively. At 1750 °C, the yield strength, compressive strength and compressive fracture strain of the Hf_0.4Ta_0.65(TaC)_0.35 alloy are 164 MPa, 186 MPa and 47.5 %, respectively. The mechanical properties of the Re_0.01Hf_0.4Ta_0.65(TaC)_0.35 alloy are basically consistent with those of the Hf_0.4Ta_0.65(TaC)_0.35 alloy, with no obvious changes. A small amount of Re has no significant effect on the phase composition of the Hf_0.4Ta_0.65(TaC)_0.35 alloy nor on its mechanical properties at 1750 °C. However, it can significantly refine the grain size and enhance the room-temperature strength and plasticity of the alloy. The two prepared alloys exhibit excellent comprehensive mechanical properties and have the potential for application in ultra-high-temperature components.