Quasi-binary Alloys Research Articles

Phase relations of the AgCdAgMg and AgCdAgZn quasibinary alloys

Phase relations of the AgCdAgMg and AgCdAgZn quasibinary alloys

Phase relation and superlattice formation in the AgZn-AgMg quasibinary alloys

The phase relation in AgZnAgMg quasibinary alloys (Ag 50Zn 50− x Mg x ternary alloys) was studied by high-temperature X-ray diffractometry and differential thermal analysis. The ζ-phase (complex hexagonal structure) which exists at low temperature in a terminal binary alloy AgZn disappears when Zn atoms of a few at. % are replaced by Mg atoms. On the other hand, the β'-phase (CsCl-type ordered structure) which is a stable phase of another terminal alloy AgMg extends to all the remaining composition. The transition temperature from the β'-phase to a β-phase (b.c.c. disordered structure) rises up rapidly with the increase of Mg content and the β'-phase becomes stable up to melting point in a composition range of more than about 25 at, % Mg. Further, a Heusler-type ordered phase appears at low temperature around a stoichiometric composition of Ag 2ZnMg. The critical temperature between the Heusler- and β'-phases has a maximum (523 K) near the stoichiometric composition. The superlattice formation of Ag 2ZnMg was discussed on a basis of the pseudopotential method. For this purpose, an expression of the structure-dependent energy was given for the ternary alloy Ag 2ZnMg. The numerical result explained satisfactorily the existence of the two types of ordered phase.

Odd-order correlations in disordered alloys: A quasi-binary approximation

The vanishing of odd-order correlations in equi-composition disordered binary alloys is generalized to include disordered quasi-binary alloys of the form A x B 1− x C. Extension of this technique to p-component alloys is indicated.

Long-period ordered structures in the quasi-binary Co3V–Ni3V alloy

Long-period ordered structures in the quasi-binary Co₃V–Ni₃V alloy

Crystalline structure of quasi-binary alloys WSE 2NBSe 2: V L Kalkihman et al, Neorg Mater, 8 (6), June 1972, 1163–1165 ( in Russian)

Crystalline structure of quasi-binary alloys WSE 2NBSe 2: V L Kalkihman et al, Neorg Mater, 8 (6), June 1972, 1163–1165 ( in Russian)

Theory of spin waves in disordered antiferromagnets. I. Application to (Mn, Co)F2and K(Mn, Co)F3

The coherent potential approximation has been extended to provide a theory of the magnetic excitations in substitutionally disordered quasi-binary antiferromagnetic alloys. It is shown how the self consistent equations for a two sublattice antiferromagnet may be reduced to a scalar form with the aid of the single site approximation and time reversal symmetry. The theory is applied to the Mn1-cCocF2 and KMn1-cCocF3 systems and numerical results obtained for comparison with recent neutron scattering experiments. The theory correctly predicts the two-peaked spectral function observed experimentally at each wavevector, and gives a good description of the dispersion relations of the two bands, and of the widths, relative intensities and lineshapes of the excitations.

A theory of disordered quasi-binary alloys

A theory of disordered quasi-binary alloys

Antifriction and electrical properties of quasi-binary WSe2-NbSe2 alloys

1. Replacing a small proportion (about 3 at. %) of the W atoms in WSe2 with Nb atoms lowers the electrical resistivity of the compound by more than two orders. 2. All quasi-binary WSe2-NbSe2 alloys, irrespective of their crystal structure, possess good antifriction properties. The coefficients of friction and wear rates of these compounds in a vacuum are one-third to one-half the corresponding values recorded under normal conditions of operation. 3. Compounds in which about 5% of the W atoms has been replaced with Nb atoms combine high electrical and antifriction properties when used in a vacuum, under normal conditions, and at high humidity. This combination of properties makes such alloys superior to all the existing conducting solid lubricants in applications in sliding electrical contacts.

A theory of disordered quasi-binary alloys

A formulation of the statistical mechanics for a quasi-binary alloy of the form A x B 1− x C is presented in which the C atoms are treated exactly, and the A and B atoms are replaced by an effective AB atom which randomly occupies lattice sites in proportion to the relative concentrations of A and B. As in the quasi-chemical approximation this formulation produces a composition-dependent interaction energy between the AB atoms and the C atoms. Static correlation functions between the AB atoms and the C atoms, which can be related back to those between A, B and C atoms, are derived in a high temperature expansion exact to the third order in T c/ T, where T c is the highest temperature at which the system shows any long range order. Contact is made to the short range order parameter, and thereby expressions for the ordering temperatures as a function of arbitrary composition and range of interaction are derived.

Temperature and Field Dependence of Magnetization of Amorphous (Fe, Mn)-P-C Alloys

Amorphous quasibinary alloys having the composition (Fe1−xMnx)0.75P0.15C0.10, where 0.0≤x≤1.0, were synthesized by rapid quenching from the liquid state. Their magnetic behavior was characterized by measurements of the magnetization as a function of temperature in the range 4.2°–300°K, and in fields ranging from 1 to 8.5 kOe. The iron-rich alloys with 0.0≤x≤0.4 are ferromagnetic: the magnetic moment at 0°K decreases linearly from 2.07 μB/Fe atom in Fe0.75P0.15C0.10 to 0.22 μB/(Fe, Mn) atom in (Fe0.6-Mn0.4)0.75P0.15C0.10. Judging from the large values of the parameter qc/qs, where qc and qs are the number per mole of magnetic carriers in the paramagnetic and ferromagnetic states, respectively, and also from the nonsaturating behavior of magnetization with field at 4.2°K, it appears that the ferromagnetism in these alloys may be of the itinerant kind. Alloys having 0.5≤x≤1.0 possess considerably more complex magnetic structures. They are characterized by a peak in the magnetization curve at temperatures between 15° and 40°K, and a ferrimagnetic-type curvature in the Curie-Weiss plots. This kind of magnetic behavior may be ascribed to ferrimagnetism existing in conjunction with parastic antiferromagnetism over some local regions in the amorphous structure.

The theory of atomic and magnetic ordering in ternary alloys with fcc lattice

We consider the theory of the mutual influence of atomic and spin ordering phenomena in ternary alloys of transition elements with fcc lattice. The case of quasibinary alloys B3A-B3D is considered in detail. Concentration dependences of the critical temperature of the order-disorder phase transition are considered for cases of atomic and magnetic ordering.

Hall effect in the ternary ordered alloys Ni3(Mn, Fe) and Ni3(Mn, Co) 1. Disordered solution solutions

An experimental study was made of the changes in the normal and anomalous Hall constants R0 and Rs, respectively, the internal saturation induction Bs, and the resistivity ϱ during the ordering of quasibinary Ni3Mn-Ni3Fe and Ni3Mn-Ni3Co alloys. The concentration dependences of R0, Rs, Bs, and ϱ were also studied in the ordered state of these alloys. It is concluded from an analysis of the experimental results that the decreases inR0 and ϱ during the ordering of Ni3Mn and as a result of the alloying of ordered Ni3Mn with slight amounts (∼5 at. %) of iron are due primarily to a decrease in the hole contribution to transport and to a decrease in the state density in the 3d band of these alloys near the Fermi level. The experimental data are in satisfactory agreement with the curve calculated by Yamashita et al. [6] for the density of 3d states in ordered Ni3Mn and Ni3Fe alloys.

Pressure-induced transformation behavior of some quasi-binary alloys of InSb

Two systems, InSbInAs and InSbGaSb, with compositions to 20 mol.% alloying compound were studied to 70 kbar at room temperature. Both InAs and GaSb additions were found to raise the transformation pressure of InSb, but each behaves differently. Possible elevated pressure phase equilibria is considered. A relationship between transformation and electronic structure is indicated based on the internal energy change at transformation being a relatively uniform perecentage of the electronic energy gap of the low pressure, semiconductor phase. Instability of the zinc-blende form at a critical percentage of the bonding energy is suggested.

Phase diagram of the alloy system Hg3Te3-In2Te3

The liquidus and solidus of the quasi-binary alloy system Hg3Te3-In2Te3 have been determined by differential thermal analysis. The phase diagram proposed is confirmed by x-ray powder diffraction analysis. Terminal solid solutions exist from Hg3Te3 to 19 mol.% In2Te3 and from In2Te3 to 86 mol.% In2Te3. Narrow regions of solid solution exist on either side of the compositions 37·5, 50 and 75 mol.% In2Te3. The maximum in the liquidus occurs at the 50% composition, where the melting is congruent.

A thermochemical study of some selected laves phases

The enthalpies of formation of MgNi 2, MgCu 2, MgZn 2, CaMg 2, SrMg 2 and BaMg 2 and of the quasibinary alloys MgCu 2-MgZn 2 were determined by means of tin solution calorimetry. For the five alloys which do not contain a transition metal, the results show a close correlation between the magnitude of the enthalpy of formation and the deviation from the ideal radius ratio (1.225); no correlation was found with the difference in electronegativity between the two components. The results for MgNi 2 show that this alloy has a significantly larger negative enthalpy of formation than the other structural prototypes, MgCu 2 and MgZn 2. This is attributed to heteropolarity resulting from a partial transfer of valence electrons from the magnesium atoms into the vacant d-levels of the nickel atoms. While the principal objective of the present work has been a study of the thermochemistry of the Laves phases, new heat of formation data are reported also for certain other intermetallic phases in the considered binary systems. We further report some new information on the heats of solution of pure nickel, magnesium, calcium, strontium and barium in liquid tin.