A nanocarbon-infused aluminum-matrix composite, termed "covetic," has been developed by Third Millennium Metals, LLC, and we have evaluated the enhanced performance prospects for strength and electrical conductivity. This paper examines the effects of the nanoscale carbon on the physical, electrical and mechanical properties of the metal-matrix composite based on microscopy, hardness, quasi-static tensile strength, high strain-rate compression strength and electrical conductivity measurements. In the as-extruded condition (warm worked at 400°F) the results show that the nanocarbon provides approximately a 30% improvement in yield strength compared to baseline 6061-T0. High strain rate, Split Hopkinson Pressure Bar (SHPB) tests revealed an opposite trend-the as-extruded covetic exhibited lower stresses at equivalent strains. In the T6 condition, the strength and ductility of 6061 with and without nanocarbon are approximately equal at all strain rates. The nanoscale carbon increased the electrical conductivity of 6061 by 43% in the as-extruded condition, but by only about 1% in the T6 condition. Electron microscopy showed that the covetic 6061 was more resistant to grain growth and coarsening during extrusion. The carbon/aluminum composite displays potential as an improved strength aluminum alloy with much higher electrical conductivity than is typical for other aluminum alloys and aluminum matrix composites.

Abstract-On the micro-scale, armature-rail interface contact is accomplished through surface asperity interaction. In this imperfect contact model (a version of the Bowden-Tabor model), we postulate the coexistence of one or more contact regimes, such as solid-solid contact, liquid-metal lubricated contact, and arcing contact. We are developing microscopic models and experimental apparatus to study this postulate. This work in particular describes the experimental apparatus developed to assist in the investigation of possible contact regimes and presents preliminary data that indicate a possible decrease in coefficient of friction in the presence of high current density when compared to a no-current condition.

We characterized the chemical, thermophysical, and mechanical properties of nanomaterials with up to 5 wt% nanocarbon (aka "covetics") in aluminum and copper metals. The nanocarbon is detectable by EDS and XPS but not by analytical methods such as LECO and GDMS. Nanocarbon raises the melting point and significantly alters surface tension, and thus porosity, during solidification. Open questions remain about the observation of higher density than would be predicted by the rule of mixtures. In aluminum alloys, we observed an increase in as-rolled strength and hardness with increasing amounts of nanocarbon. In copper, thermal conductivity was anisotropic: up to 50% higher in the extrusion direction and at least 25% lower in the transverse direction, and was different between transient and steady state test conditions. In aluminum, we observed a significant increase in electrical conductivity with nanocarbon, from 47 to 67% IACS. These materials are commercially promising because they are produced by conversion of inexpensive carbon powder to nanocarbon in the meltpaving the way for the production of nanomaterials in pyrometallurgical operations with economies of scale.

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