Microstructural evolution and exceptional high-temperature stability of an in situ synthesized Cu-V6C5 composite

Abstract

Abstract

A novel copper matrix composite reinforced in situ with vanadium carbide V 6 C 5 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/cm 3 ) free of residual porosity. Synchrotron high-energy X-ray diffraction (HEXRD) combined with thermodynamic calculations confirmed the in situ precipitation of non-stoichiometric V 6 C 5 as the predominant equilibrium carbide phase. Microstructural analyses (SEM/EBSD/TEM) revealed a distinct bimodal grain architecture consisting of coarse unreinforced Cu grains ( μm) and ultrafine-grained Cu regions ( nm) pinned by a fine dispersion of nanoscale rounded ( nm) to submicrometer faceted V 6 C 5 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 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 V 6 C 5 composite as a highly promising candidate for high-temperature and high-heat-flux components in future fusion reactors.