Tensile behavior of carbon nano-fiber-reinforced Cu composite using the liquid infiltration process
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. INTRODUCTION
AT present, there is a great demand for high-strength and high-conductivity connector materials in the electronics industry.[1–10] For the development of such connector materials, various fabrication routes have been explored to strengthen the pure Cu (which is the most widely used connector material) by nonalloying methods in order to not sacrifice the electrical conductivity. Among them, the severe plastic deformation of pure Cu and the Cu composite reinforced with carbon nano fiber (CNFs) have attracted great interest.[1,6,7,11–14] Theoretically, the tensile strength of over 1000 MPa and the international annealed-copper standard value of 80 pct could be obtained with the Cu composite reinforced with 20 pct CNF, assuming a perfect bonding between the Cu and CNF. The powder metallurgy (PM) route is the currently available fabrication method for the nano-sized-fiber-reinforced metal-matrix composite (MMC).[7,14] The PM technique has, however, an inherently low productivity and high processing cost. The liquid infiltration technique has a variety of advantages compared to the PM technique, including high productivity and possible near-net shaping.[14] However, the liquid infiltration technique has been considered impossible for the fabrication of nano-sized-fiber-reinforced MMCs, since the applied pressure must be extremely high.[14] Previously, the authors conducted
a theoretical calculation to obtain the minimum pressure required for a Cu melt to infiltrate through a CNF bundle, considering surface tension, flow resistance, and the compaction of the CNF bundle during pressing, and reported that the fabrication of a CNF-reinforced Cu composite was possible by the liquid infiltration process at a pressure as low as 20 MPa by employing a simple hydrostatic pressurization principle.[15] Previously, no attempts have been made to fabricate the nano-fiber-reinforced MMC by the liquid infiltration technique. For the successful fabrication of a CNFreinforced Cu composite, many things need to be solved.[14–18] Most significantly, the unidirectional alignment of the CNF must be accomplished for the maximum effect of the reinforcement. The interfacial relationship between the CNF and Cu must be also established.[8,16] In the present study, the CNF-reinforced Cu composite was fabricated by the liquid infiltration process, and the tensile behavior of the fabricated composite was evaluated. The descriptions of the fiber alignment process and the liquid infiltration process were given. The deformation behavior of the composite was discussed based on the scanning electron microscope (SEM) fractographs. Finally, the strengthening mechanism for the CNF-Cu composite was proposed based on the transmission electron microscope (TEM) microscopic observations. II. EXPERIMENTAL PROCEDURES
YOUNGHWAN JANG, Graduate Student, and SANGSHIK KIM, Associate Professor, are with the Division of Materials Science and Engineering, Engineering Research Institute, Gyeongsang National University, Chinju 660-701, Korea. Contact e-mail: sa
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