Study On Fabrication, Microstructure And Properties Of Discontinuous C_f/Cu Composites

Discontinuous Cf/Cu composite, with its peculiar properties of high electrical-conductivity, high thermal-conductivity, self-lubricating, resisting electric-arc erosion and so on, is a prospectively functional composite. In the process of fabricating the composite, there are two key technical questions , that is the wetting quality and even-distribution of carbon fibers in matrix. In the study, powder metallurgy was adopted to fabricate discontinuous Cf /Cu composite. The surface treatment of carbon fibers and fabricating technology of the composite were two keys of the study. And microstructure and properties of the material were also researched more systemically.In the study, several ways were adopted for surface oxidation treatment of carbon fibers to improve binding strength between copper coating and carbon fibers. Final results indicated that the way being fit for plating copper on the surface of carbon fibers was that carbon fibers were oxidized in hot air and boiled in nitric acid at high temperature. To settle the wetting quality between carbon fibers and copper matrix, several solutions were used to treat with the surface of carbon fibers. A lot of experiments showed that the surface of carbon fibers might gain high quality plating copper coating in citrate solution and craft parameters of plating had great influence on plating copper.Several dispersants were used for mixing with carbon fibers and copper powders. The experiment showed that (glycerin + alcohol) was an optimal dispersant used for fabrication of discontinuous Cf /Cu composite, because it could redound to well-distributing of carbon fibers in the matrix. By analyzing microstructure and morphology of the composites at the different pressure and different sintering temperature, optimal craft parameters of primary pressing-sintering were ascertained: 350MPa (pressing) + 400 C + lh (clearing gas) + 800 C + 40min (sintering).After primary press, the carbon fibers showed some directional distribution.The composite was pressed and sintered again to further enhance its synthetical properties. Through this treatment, interface binding strength, compactness, conductivity and mechanical properties of the composite were prominently increased. The analysis of microstructureindicated that there were still certain amount of holes, so its density and conductivity were evidently under theoretic value. Based on the reason, the fabricating technology of the composite needed further perfecting. Through testing the wear and tear properties, analyzing the mechanism of wear, results showed that carbon fibers were in favor of enhancing antifriction and wear-resist properties of the discontinuous Cf /Cu composite.