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Abstract:
Copper-matrix composites reinforced with silicon carbide (SiC) particles are heat sink materials with potential application in the electronic industry. A major challenge in the manufacturing of these materials, involving sintering process, is to prevent the decomposition of SiC and the subsequent dissolution of silicon in the copper matrix. This is overcome by coating SiC particles with metallic layers. In this study, a combined experimental and computational micromechanics approach was used to investigate thermal conductivity of Cu-matrix composites reinforced with silicon carbide particles coated with chromium, titanium, or tungsten layers. Plasma Vapor Deposition (PVD) was used to produce the metallic layers on SiC particles, while Spark Plasma Sintering (SPS) to consolidate the powder mixtures of copper and coated silicon carbide. Thermal conductivities of the fabricated three-phase composites Cu/SiC/Cr, Cu/SiC/Ti and Cu/SiC/W were evaluated using the Laser Flash technique. Finite Element Method (FEM) and Variational Asymptotic Method (VAM) based homogenization techniques were used for computational modeling of thermal conductivity. In the numerical models complex material microstructures were accounted for using micro-CT images of the sintered compacts. Comparison of the experimental results with simulations highlighted the importance of including the effect of imperfect interfaces to accurately model thermal conductivity of the investigated composites.

Keywords:
metal-matrix composites, powder metallurgy, plasma vapor deposition, imperfect interface, thermal conductivity, numerical modeling

Abstract:
This work presents a combined experimental and computational study of the deformation and fracture of microcantilever specimens made of chromium(rhenium)-alumina metal–matrix composite (MMC), with a particular focus on the failure properties of the metal–ceramic interfaces. The obtained experimental results show that the bending strength of microcantilevers containing alumina particles in critical cross-sections near specimen's fixed end is considerably higher than that of unreinforced chromium(rhenium) samples. Brittle cracking along chromium–alumina interfaces is the dominant fracture mode of the composite microcantilevers. The interface characteristics are determined in an indirect way by numerical simulations of the experiment with account of the actual specimen microstructure from the scanning electron microscope (SEM) images. A parametric study demonstrates that the overall material response may be reproduced by different sets of model parameters, whereas the actual failure mode permits to discriminate among the possible alternatives. Using this approach, the in situ values of the chromium–alumina interface cohesive strength and the fracture energy are estimated.