Thermodynamic and Kinetic Justification of a Processing Route for Nanostructured W–Cu Composites Produced by Mechanical Activation and Spark Plasma Sintering

Nanostructured tungsten–copper (W–Cu) composites are promising materials for high-heat-flux components and advanced thermal management; however, their processing is limited by a high positive enthalpy of mixing of ~35.5 kJ/mol and weak interfacial bonding. This study provides a thermodynamic and kinetic justification for a technological route intended for 70W–30Cu and 75W–25Cu (wt.%) composites using high-energy mechanical activation and spark plasma sintering (SPS). CALPHAD-type calculations identified a critical copper activity plateau aCu ≈ 0.33 at 950 °C in the W-rich range, which favors the retention of submicron grains of 200–300 nm by limiting the chemical potential driving force for coarsening. Kinetic modeling via DICTRA predicted the formation of metastable interfacial diffusion zones with a characteristic width of 20–90 nm during short SPS holding times of 150–300 s, enabling the transition from mechanical interlocking to metallurgical bonding. Based on these calculations, a processing window of 950–1050 °C is proposed to achieve a target relative density of ≥97% and electrical conductivity of 35–45% IACS. The results provide a predictive framework for the experimental synthesis of nanostructured pseudoalloys with optimized conductive networks and reinforced tungsten skeletons.