Abstract:

The rapid expansion of marine industries has created an urgent demand for advanced engineering materials with superior multifunctional performance. While Cu-Ni alloys demonstrate favorable stability and tribological characteristics, their practical applications are constrained by compromised thermal conductivity and insufficient mechanical strength due to the solid solution of a high amount of Ni in the Cu matrix. Cu-Ni matrix composites reinforced with hexagonal boron nitride (h-BN) have garnered significant attention due to their potential for tailored mechanical and thermal properties. However, challenges such as BN agglomerations in Cu-Ni matrix and poor interfacial bonding hinder their practical applications. To address these limitations, this study proposes an innovative fabrication strategy for boron nitride nanosheets (BNNSs) reinforced Cu-Ni composites by integrating the in situ synthesis of BNNSs on Cu powders via chemical vapor deposition with powder metallurgy. Benefited by the in situ strategy, BNNSs with high crystallinity distribute uniformly within the Cu matrix and have an intimate interfacial bonding without voids or other types of defects. Remarkably, the BNNSs/Cu-30%Ni composite achieves simultaneous enhancement in strength and ductility, exhibiting an ultimate tensile strength of 417 MPa and fracture elongation of 17.5%, representing 30% and 118% improvements over pure Cu-Ni alloys, respectively. This exceptional mechanical synergy originates from threefold strengthening mechanisms: grain refinement, mobile dislocation pinning, and efficient stress transfer via robust interfaces. The microstructural analysis confirms that homogenous distribution of BNNSs optimized stress distribution, mitigating strain localization in the composites. Fractographic examination demonstrates uniformly distributed dimples containing embedded BNNSs, indicative of effective crack bridging and deflection during failure. Furthermore, the composite possesses excellent corrosion resistance comparable to matrix alloys, while achieving 21.23% enhancement in thermal conductivity and 20% reduction in coefficient of friction. The scalable fabrication protocol successfully resolves longstanding challenges in BNNSs dispersion and interfacial bonding, offering a viable pathway for designing high-performance CMCs for marine applications.

Key words: Cu-Ni matrix composites, Boron nitride nanosheets (BNNSs), In situ chemical vapor deposition, Interfacial bonding, Mechanical properties