Thermal conductivity and microstructure of graphite flakes reinforced titanium matrix composites fabricated by spark plasma sintering

Abstract

In this study, pure titanium (Ti) and Ti-6Al-4 V (TC4) matrix composites reinforced with 50 vol% graphite flake (GF) were fabricated by spark plasma sintering (SPS) respectively. The effects of different matrix and sintering temperatures on the microstructure and thermal conductivity (λ) of the composites were systematically investigated. The results showed that the interfacial reaction between the GF and pure Ti or TC4 produced an intermediate layer of titanium carbide (TiC). The thickness of TiC layer in both composites increased with the sintering temperature. At the same sintering temperature, the thickness of interface reaction layer TiC in GF/TC4 composite was much lower than that in GF/Ti composite, which also made the λ of the former significantly higher than that of the latter. The best sintering temperature of the two composites was 1150 °C. Under this condition, the λ of 50 vol% GF/TC4 composite reached 185.03 W m−1 K−1, which is more than 25 times of the λ of the matrix. It is expected to solve the problem of low λ of Ti materials used in plate heat exchangers.