O.N. Carlson

Electrotransport of interstitial atoms in yttrium

Abstract The electrotransport velocities of carbon, oxygen and nitrogen in yttrium were determined in the temperature range of 1235 to 1460°C. Diffusion coefficients and effective charges were calculated for these elements for the same temperatures. Yttrium metal purified by the electrotransport method showed a decrease in oxygen content from 780 to 90 p.p.m. and an increase in the resistance ratio from 12 to 45.

The yttrium-germanium system

Abstract The yttrium-germanium system has been investigated by thermal, microscopic, chemical and X-ray analyses. Germanium lowers the transformation temperature of yttrium from 1473 °C to 1460 °C by an inverse peritectic reaction. There is a eutectic reaction at 12 at. % germanium and 1280 °C between yttrium and the compound Y5Ge3, which melts congruently at 1965 °C. Another eutectic occurs at 88 at. % germanium and 820 °C between germanium and YGe3.5, which forms peritectically at 860 °C. There are six additional compounds in the system that result from peritectic reactions, namely, Y5Ge44 at 1945 °C; Y11Ge10 at 1900 °C; YGe at 1730 °C; Y2Ge3 at 1460 °C; YGe1.7 at 910 °C and YGe2 at 880 °C. The compound Y2Ge3 undergoes a polymorphic transformation at 1430 °C. New evidence concerning the crystal structures of Y2Ge2 and YGe1.7 which involve the A1B2 defect and the ThSi2 defect structure types, respectively, was obtained. The compounds YGe2 and YGe3.5 decompose eutectoidally at 760 °C and 710 °C, respectively, and their crystal structures are discussed.

The vanadium-nitrogen system: a review

This paper is a critical review of the available phase equilibria, crystallographic, and thermodynamic data for the vanadium-nitrogen system. Three nitride phases, βV2 N1-y, δVN1-x, and δVN1-x, have been identified and their crystal structures, ranges of homogeneity, and melting or decomposition temperatures determined. The sol vus boundary for the vanadium-rich solid solution is placed at 3.8 at. pct N at 550 °C and increases to 11 at. pct N at 1500 °C. A break in the solvus observed at 550 °C is associated with the formation of a metastable phase, V16N. Other metastable phases have been identified, but their exact stoichiometries and structures have not been unambiguously determined. The enthalpies and free energies of formation, heat capacities, and dissociation pressures for the subnitride and mononitride are evaluated and correlated.

ELECTROTRANSPORT OF CARBON IN NIOBIUM AND TANTALUM.

The electrotransport velocity of carbon in niobium and tantalum was measured at temperatures above 1900 °C using 14C as a tracer. In both metals carbon was found to migrate in the opposite direction to the electron flow. The diffusion coefficients and effective charge were also calculated for this solute at the same temperatures. A least-squares treatment was made of the combined diffusion data of this study and that obtained at lower temperatures by other investigators. Values of D0 and ΔH in the equation D = D0 exp (-gDH/RT), were determined for the extended temperature range and are as follows; niobium tantalum.

Solid solubilities of oxygen, carbon and nitrogen in yttrium

Abstract The solid solubilities of oxygen, carbon and nitrogen in yttrium metal have been investigated and a partial diagram is proposed for the Y-YN system. The temperature dependence of the solubility of each solute in α yttrium was fitted empirically to Arrhenius-type equations, and the heats of solution for the co-existing oxide, carbide or nitride phase were found to be 6.8 ± 0.4, 8.0 ± 1.0 and 11.6 ± 1.3 kcal/mole, respectively.

Purification of rare-earth metals by electrotransport

Abstract The principles of the electrotransport purification process are described, together with those variables that affect the degree of purity attainable. Experiments on the purification of yttrium, lutetium and gadolinium with respect to carbon, nitrogen and oxygen are described and the results compared with those predicted from theory. Metal purities were evaluated by resistance ratio measurements and chemical analyses.

ELECTROTRANSPORT PURIFICATION AND SOME CHARACTERIZATION STUDIES OF VANADIUM METAL.

High-purity vanadium metal having an interstitial impurity content of <5 wt ppm and a resistance ratio,R300 K/R4.2 K, of >1880 has been prepared by an electrotransport technique. The lattice parameter of vanadium of this purity is 3.0269 +- 3Å. An extrapolated value for the room temperature resolved flow stress of vanadium free of C, O, and N was determined to be 0.41 kg/mm2 on this material.

The yttrium-cobalt system☆

Abstract A constitutional diagram for the yttrium-cobalt system is proposed based upon microscopic evidence, thermal analyses and X-ray diffraction data. Evidence was found for the occurrence of nine intermetallic compounds in this system. The structures of three of these, YCo 5 , YCo 3 and YCo 2 have been determined and six other intermediate phases were tentatively identified as having the compositions, Y 2 Co 17 , YCo 4 , Y 2 Co 3 , YCo, Y 3 Co 2 and Y 3 Co. Eutectic reactions occur at 1340°C and 93 at. % Co and at 725°C and 37.5 at. % Co. There appears to be negligible solid solubility of yttrium in cobalt.

The effect of low percentage alloying additions on the ductility of iodide chromium

Abstract The ductility of binary chromium-base alloys containing 0.1, 0.5, 1.5, and 3.0 wt. % of 34 different metals was evaluated from bend tests on arc-melted specimens. The results of this investigation indicate that the brittle-ductile transition temperature of chromium-base alloys is dependent primarily on the atomic size of the alloying addition. The transition temperature of iodide chromium is decreased by the addition of solute atoms that form solid solution alloys and have atomic diameters larger than chromium but not exceeding the 15% size limit. Those elements with atomic diameters between 2 and 10% larger produce the maximum decrease in the brittle-ductile transition temperature. Those alloying additions which exhibit little or no solid solubility in chromium and have atomic diameters that exceed the 15% limit all raise the transition temperature of high purity chromium. Additions of those metals that form carbides, nitrides, and oxides that are more stable than the corresponding chromium compounds increase the brittle-ductile transition temperature rather sharply, which is the converse of what has previously been observed on chromium of lesser purity.

The Hafnium-chromium system

Abstract A phase diagram is proposed for the hafnium-chromium system based on the results of microscopic, X-ray and thermal analyses. The main features of the diagram are: a Laves phase, HfCr2, which melts congruently at 1825 °C and undergoes a crystallographic transformation between 1320 ° and 1360 °C; eutectic reactions at 1480 °C and 29 at.% Cr and 1660 °C and 86 at.% Cr; and a eutectoid reaction at 1390 °C and 12 at.% Cr. It was confirmed that the stable form of HfCr2 at low temperatures has the face-centered cubic, MgCu2-type structure, while at high temperatures it has the hexagonal MgZn2 structure.