A novel copper matrix composite reinforced in situ with vanadium carbide V6C5 was successfully synthesized via mechanical alloying and hot isostatic pressing (HIP) to address the operational temperature limitations of conventional CuCrZr heat-sink alloys in nuclear fusion applications. Elemental Cu, V, and C powders were milled for 40 h, achieving optimal crystallite refinement and precursor homogeneity. A subsequent thermochemical reduction in an Ar-10%H atmosphere effectively reduced oxygen contamination down to 0.047 wt%. Following degassing, consolidation by HIP at 1050 °C and 180 MPa produced a fully dense material (8.30 g/cm3) free of residual porosity. Synchrotron high-energy X-ray diffraction (HEXRD) combined with thermodynamic calculations confirmed the in situ precipitation of non-stoichiometric V6C5 as the predominant equilibrium carbide phase. Microstructural analyses (SEM/EBSD/TEM) revealed a distinct bimodal grain architecture consisting of coarse unreinforced Cu grains (∼8 μm) and ultrafine-grained Cu regions (∼231 nm) pinned by a fine dispersion of nanoscale rounded (3−15 nm) to submicrometer faceted V6C5 particles. Mechanical properties were evaluated by microhardness, nanohardness and profilometry-based indentation plastometry. The consolidated composite demonstrated exceptional thermal stability, retaining an elevated hardness of 2.11±0.03 GPa up to 800–900 °C without detectable microstructural coarsening, with grain growth and softening setting in only above 950 °C. These results position the in situ processed V6C5 composite as a highly promising candidate for high-temperature and high-heat-flux components in future fusion reactors.
