Group IVA Metals Research Articles

Nickel and cobalt eutectic alloys reinforced by refractory metal carbides

Eutectiferous behavior was observed within pseudobinary joins between the monocarbides of the group IVa and Va metals with nickel and cobalt. Coupled two phase growth normal to a macroscopically planar liquid-solid interface was noted even though the various carbide phases grew in a faceted manner. The composite structures formed by unidirectional freezing consisted of either a cobalt or nickel matrix with an aligned whisker-like or three-sided lamellar carbide dispersion. The nickel-niobium monocarbide system was examined in greatest detail and found to be stronger than TD nickel in tension from room temperature to 2100°F. Repeated fracture along the length of individual carbide whiskers was observed during tensile straining. This behavior, which is nontypical of previous eutectic whisker composites, was interpreted in terms of the distribution in whisker strengths. The strength of extracted NbC whiskers measured in bending was found to approach the theoretical failure stress. Creep rupture tests further indicated that reinforcement of a weak nickel or cobalt matrix with aligned monocarbide whiskers provides a new type of material for use at elevated temperatures.

Galvanomagnetic properties of certain hard refractory compounds of group IVA metals in the two-band representation

On the basic of a study of the galvanomagnetic properties of certain refractory compounds of group IVA metals it is concluded that the theory of galvanomagnetic effects derived for metals can be applied to metal-like compounds. The experimental information available shows that the two-band model yields relatively definite conclusions regarding the mechanism for the electrical connectivity of these compounds.

Magnetoresistance and Hall effect of carbides of the group IVA metals

Magnetoresistance and Hall effect of carbides of the group IVA metals

Magnetic Susceptibility and Energy Band Structure of Zirconium Monocarbide

AbstractThe magnetic susceptibility of zirconium monocarbide has been studied as a function of temperature and concentration in the homogeneity region 0.58 ≦ x ≦ 1.0 and at temperatures from 20 to 1300 °K. It is shown that the temperature dependence χ(T) of all the samples may be described by the equations The obtained results are discussed in terms of concepts available on the electronic structure of the cubic carbides of the group IVa and Va transition metals. A “flat” minimum was found in the curve N(E) lying near stoichiometric composition of the monocarbides.

Low-Temperature Specific Heats of Titanium, Zirconium, and Hafnium

The specific heats of titanium, zirconium, and hafnium were found to obey the relation $c=\ensuremath{\gamma}T+\ensuremath{\beta}{T}^{3}$ from 1.1 to 4.5\ifmmode^\circ\else\textdegree\fi{}K within the experimental error. As in other transition metals, the electronic term is large and for the Group IV-A metals decreases with increasing atomic number indicating a progressively larger degree of electronic interaction in the sequence titanium, zirconium, and hafnium. The Debye temperatures decrease with increasing atomic mass as would be expected from the central-force model; however, the ratio of the Debye temperatures indicate that the average atomic force constant for hafnium is some 50% larger than for titanium and zirconium in agreement with the unusually small atomic volume of hafnium.

The heats of formation of some transition metal silicides

A method is described for determining the heats of formation of highly stable metal silicides and data are given for the following compounds: —Ti 5Si 3, TiSi, TiSi 2, Zr 5Si 3, ZrSi, ZrSi 3, ThSi 2, V 2Si, TaSi 3, Ta.Si 2, MoSi 2, and WSi 2. The highest heats of formation are those of compounds containing Group IVa metals and, in general, the disilicides are not as stable as compounds containing a lower percentage of silicon. An analysis of the bond lengths in the disilicides is carried out and a comparison is made between the heats of formation data and changes in the character of the metal bonding.