Microstructure and thermal properties of copper matrix composites reinforced with titanium-coated graphite fibers

Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopies, and by measuring thermal properties, including thermal conductivity and coefficient of thermal expansion (CTE). The results show that the milled fibers are preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composites. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer. This carbide layer establishes a good metallurgical interfacial bonding in the composites, which can improve the thermal properties effectively. When the fiber content ranges from 35 vol% to 50 vol%, the in-plane thermal conductivities of the composites increase from 383 to 407 W center dot(m center dot K)(-1), and the in-plane CTEs decrease from 9.5 x 10(-6) to 6.3 x 10(-6) K-1. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer during sintering process. This TiC interlayer caused the interface structure of the graphite fiber/Cu composite to change from mechanical bonding into metallurgical bonding, which can improve the thermal properties effectively.