Interface formation evolution of the hot-forged copper-(Cr)diamond composite and its thermal conductivity

Due to the distinction of (111) and (100) faces on the diamond particle, the preferential formation of in-terface layers on the diamond particle is discovered when adding metal additives like titanium, chromium, aluminum in copper/diamond composites. The formed interface would affect the thermal conductivity of the copper/diamond composites. In this study, copper-55 vol%(Cr-coated) diamond composites were suc-cessfully produced by hot forging under 800 degrees C, 900 degrees C and 1050 degrees C. Heat treatment of Cr-coated diamond powders was conducted under a series of temperatures for studying the evolution of the carbide interface formation on surfaces of diamond particles. It was found that the average grain size of the Cr7C3 on diamond (111) faces was larger than that on (100) faces when the temperature is below 850 degrees C, and the opposite trend was observed when the heat treatment temperature is above 850 degrees C. The Cr layer was fully transformed into Cr7C3 when the temperature was above 950 degrees C. Unlike the results obtained after heat treatment, the in-terface layers was directly transformed into Cr3C2 due to the non-equilibrium phase transformation after hot forging. The Cr3C2 interface layers were preferentially kept on (100) diamond faces, and exfoliated on (111) faces after hot forging. The grain size of the formed Cr3C2 on diamond (100) faces was increased with raising the hot forging temperature. The 1050 degrees C-hot-forged sample showed the highest thermal con-ductivity, attributed to large grain sizes of the Cr3C2 interface layer. This study elaborates the mechanisms of the evolution of the interface layer formed under different temperatures on the diamond surfaces in copper-(Cr-coated) diamond composites, and the phenomenon of preferential formation of the interface layers is verified.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

Due to the distinction of (111) and (100) faces, metal additives preferentially form interface layers on diamond particles in copper/diamond composites. The interface layers formed can affect the thermal conductivity of the composites. Copper-55 vol%(Cr-coated) diamond composites were produced by hot forging under different temperatures, and the evolution of the carbide interface formation on diamond surfaces was studied. Different behavior was observed below and above 850 degrees C, and the thermal conductivity was highest for the sample hot forged at 1050 degrees C.