Some studies on the V-C system

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1984
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Ghaneya, Abdel
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Materials Science and Engineering
Materials engineers create new materials and improve existing materials. Everything is limited by the materials that are used to produce it. Materials engineers understand the relationship between the properties of a material and its internal structure — from the macro level down to the atomic level. The better the materials, the better the end result — it’s as simple as that.
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The present study consists of a comprehensive critical review of the data in the literature on the V-C system together with experimental work on some areas of uncertainty in the V-C diagram. The combined results are the basis for a proposed revised V-C phase diagram;The (zeta) phase carbide was prepared by annealing a V-39.67 at. % C alloy at 1300(DEGREES)C for 220 h in a vacuum furnace. A hexagonal crystal structure with a = 2.9185 (+OR-) 0.002 (ANGSTROM) and c = 27.788 (+OR-) 0.03 (ANGSTROM) was obtained for this phase from its x-ray powder diffraction data. The peritectoid decomposition temperature was determined as 1320 (+OR-) 5(DEGREES)C by differential thermal analysis. From x-ray, metallographic, and chemical analyses, the stoichiometric composition of the (zeta) phase was determined as V(,4)C(,2.62) or (TURNEQ) V(,3)C(,2);The solvus curve for the V-rich end of the V-C system was determined by equilibrating vanadium with carbon powder at temperatures between 1100 and 1500(DEGREES)C. The maximum solubility of C in V was obtained from the results of the solubility studies as 4.5 at. % C at 1665(DEGREES)C;The composition and temperature of the VC-C eutectic alloy were experimentally determined to be 49.2 at. % C and 2645 (+OR-) 25(DEGREES)C, respectively, in agreement with published data;No evidence to support the postulated existence of an ordered V(,64)C phase was found from TEM, microscopic, or electron diffraction analyses of the matrix and precipitate phases;An attempt was made to calculate the contribution of carbon to the residual resistivity of vanadium. A value for (rho)' of 4.0 (+OR-) 1.9 x 10('-10) ohm-cm/at. ppm was obtained from the measurement of residual resistivity ratios (RRR) as a function of carbon concentration;Crystal structures data and thermodynamic properties of the reported phases of the V-C system available from the published literature are tabulated and evaluated.

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Sun Jan 01 00:00:00 UTC 1984