Interface manipulation and its effects on the resultant thermal conductivity of hot-forged copper/Ti-coated diamond composites

Abstract

Copper/55 vol%Ti-coated diamond composites are successfully fabricated by hot forging from pure copper powder and Ti-coated diamond particles, and the interphase layer structure of the composites are influenced by the pre-annealing Ti-coated diamond particles. It shows that the diamond particles start to react with the Ti coating to form TiC phase at 800 °C, and the reaction is activated first on the diamond-{111} facets, attributed to the sp3 -hybridized crystal structure transforming into relatively disordered and highly active sp2 -hybridized crystal structure (graphite cluster), and this leads to anisotropy structures are formed between the diamond-{100} and -{111} facets for the 800 °C-annealed Ti-coated diamond particles. With increasing the annealing temperature to 900 °C and 1050 °C, diamond-{100} become more active and there are more nucleation sites to form TiC particles due to the formation of the diamond-{111} facet on the diamond-{100} surface and the carbon atoms are easier to be freed on the diamond-{100} compared to diamond-{111}, and the microstructural difference between diamond-{100} and -{111} facets are significantly reduced. In-situ formation of TiC particles during hot forging process enables to form strong interface bond between the diamond and the copper matrix for Ti-800 °C-Cu/Dia, attributed to the diamond has high TiC interface coverage rate (about 79.5%), intact contact interface between the diamond and the copper, and rough surface of the formed interphase layer. These lead to the Ti-800 °C-Cu/Dia has the highest thermal conductivity (about 350 W/(mK)) among the three fabricated copper/diamond composites. This research provides insight on copper/diamond composite’s interface formation mechanisms and manipulation for regulating the thermal conductivity property.