Ronald C. Rossi

The tensile properties of a graphite-fiber-reinforced Al-Si alloy

Room temperature uniaxial tensile tests have shown that composites of an Al-13 wt pct Si alloy and Thornel 50 graphite fibers have strengths greater than a theoretical value that was calculated on the basis of the law of mixtures. At 28 vol pct fibers, the average uniaxial tensile strength was found to be 106,000 psi, and several values between 130,000 and 144,000 psi were obtained. The modes of deformation and failure in the composites have been studied by the microexamination of polished surfaces and fractures of tested specimens. The reasons for the high strengths and the unusual modes of fracture that were observed cannot be explained on the basis of the presented data. Specimens of the composite have been thermally cycled between −193° and +20°C twenty times and others between −193° and +500°C twenty times. Tensile tests and microexamination of these thermally cycled specimens show that thermal cycling does not degrade the tensile properties of the composites or change their microstructure.

ELASTIC PROPERTIES OF ISOTROPIC GRAPHITE.

Abstract Youngs modulus and the shear modulus (at room temperature) are reported for the first time for bulk isotropic graphites of various porosities. Extrapolations to zero porosity indicate Youngs modulus and the shear modulus of theoretically dense isotropic graphite to be 255 kilobars and 97 kilobars respectively. Poissons ratio for fully dense isotropic graphite is 0·31 compared with previous literature values of 0·14 and less.

Microstructures of zirconium-based ternary carbide alloysa

Abstract The microstructures of the zirconium carbide-graphite alloys were characterized, and the effect of ternary additions on the microstructure of a high-carbon base alloy was studied. Minor variations of carbon content in the vicinity of the eutectic composition produced gross microstructural changes. The addition of boron produced a coarsening of the microstructure, and the combined addition of magnesium and silicon produced graphite nodules. The addition of tantalum carbide caused major alterations of the microstructure with the complete loss of characteristic features at high additive concentrations.