This study focuses on the powder processing methodology (PPM) for the fabrication of metal matrix composite using Graphite flakes (Grf) reinforced Copper (Cu). The manufacturing route involved 1) a reductive treatment of Grf powder to purify and increase its quality, 2) the mixing of the Cu and the Grf (0 to 40 vol.%) powders with a fast and efficient resonant acoustic (RA) mixer, and finally 3) the cold and hot-pressing of composite powders. Comparison of PPM is made with literature and a usual method used in our laboratory. The quality of Grf after different steps was analyzed by Raman spectroscopy and phase compositions and microstructure of the composite materials were analyzed by XRD and SEM, respectively. It was shown that this new PPM demonstrated better composite structural and thermal properties even at low volume fraction of Grf with a maximum of 630 W.m-1 .K-1 obtained with 40 vol.% of Grf at 70 °C. This was possible thanks to our new PPM which allows getting lower defects in the Carbon lattice of Grf and oxygen content in the final composite materials.
pression is not yet available in the literature and conventional models which have been developed to describe the This paper investigates die compression of tungsten compressibility of powder never refer to WC-Co mixtures. carbide-cobalt powder mixtures, which is an import-In this context, the present study is an attempt to obtain a ant step in the processing route of cemented carbides.better characterisation and understanding of the pressing Simple action compression of miscellaneous mixtures of these mixtures. It focuses on die pressing, which is the has been investigated with an industrial type press most classical pressing technique. allowing measurement of the force applied on both Because of the friction between the powder and the die, upper and lower punches. In addition, an original the state of stress within the powder is not homogeneous apparatus was used to measure the average radial during die pressing. Thus, the interpretation of data drawn stress applied upon the die, and the frictional shearing from this test requires a mechanical analysis. A simple force at the powder/die interface was determined model, which has already been used by Mosbah et al.1 for through a powder/wall friction apparatus. A mechaninvestigating the compressibility of iron powder, is proposed ical analysis of the data obtained for various tungsten for this purpose. This analysis, which is supposed to provide carbide-cobalt powder mixtures provided the intrinthe intrinsic compressibility law of the material, is validated sic stress v. density compressibility relation as well by comparing results of tests performed with several as the radial stress transmission coefficient and the devices, as well as data obtained with compacts of different powder/die friction coefficient. In this framework, the geometries. effect of several material and process parameters on With the help of this model, the influence of material the densification is discussed.PM/0825 parameters (cobalt content, carbide grain size) and process parameters (granulation, compression rate) on the com-At the time the work was carried out Dr Roure pressibility of WC-Co systems is investigated and the was with the Centre Europe ´en de Recherches en mechanisms responsible for this behaviour are discussed. Me ´tallurgie des Poudres,
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