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

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 (lambda) of the composites were sys-tematically 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 lambda of the former significantly higher than that of the latter. The best sintering temperature of the two com-posites was 1150 degrees C. Under this condition, the lambda of 50 vol% GF/TC4 composite reached 185.03 W m-1 K-1, which is more than 25 times of the lambda of the matrix. It is expected to solve the problem of low lambda of Ti materials used in plate heat exchangers. (c) 2022 Elsevier B.V. All rights reserved.