Effect of chromium carbide coating on thermal properties of short graphite fiber/Al composites

A chromium carbide coating was synthesized onto graphite fibers by molten salts method to improve the interfacial bonding and thermal properties of short graphite fiber/Al composites which were fabricated by vacuum pressure infiltration technique. The graphite fiber/Al composites with different thicknesses of chromium carbide coatings were prepared through varying plating times to investigate the influence of chromium carbide layer on the microstructures and thermal properties of the composites. The combined Maxwell–Garnett effective medium approach and acoustic mismatch model schemes were used to theoretically predict thermal conductivities of the composites. The results indicated that the chromium carbide coating formed on graphite fiber surface in molten salts consists mainly of the Cr₇C₃ phase. The Cr₇C₃-coating layer with plating time of 60 min and thickness of 0.5 μm was found to be most effective in improving the interfacial bonding and decreasing the interfacial thermal resistance between graphite fiber and aluminum matrix. The 40 vol% Cr₇C₃-coated graphite fiber/Al composite with Cr₇C₃ thickness of 0.5 μm exhibited 45.4 % enhancement in in-plane thermal conductivity of 221 W m⁻¹ K⁻¹ compared to that of uncoated composite, as well as the coefficient of thermal expansion of 9.4 × 10⁻⁶ K⁻¹, which made it as very interesting material for thermal management applications.