Binary Alloy Phase Diagrams Research Articles

Ab-Initio Calojiations of Phase Diagrams of Binary Simplemetal Alloys

ABSTRACTThe combined application of electronic and thermodynamic perturbation theories allows for an ab-initio calculation of the phase diagrams of binary simple-metal alloys.

Monte carlo study of the phase diagrams of binary alloys with face centered cubic lattice structure

We describe the results of Monte Carlo computations of the coherent phase diagram (in the temperature-composition plane) of ordering binary alloys on an f.c.c. lattice. Results on long- and short-range order parameters as well as ordering energies are also given. We consider the system with nearest neighbor interaction in the grand-canonical ensemble (equivalent to an Ising antiferromagnet in a magnetic field) as well as in the canonical ensemble (fixed composition). The close agreement between both approaches serves as a severe test of the good accuracy obtained, and so does the fact that differences between results for lattices with 2048 sites and with 16384 sites are found to be negligibly small. Results with next-nearest neighbor interaction are also given, and for both models a comparison with other available predictions is made, particularly with the cluster-variation method. While the latter is found to be quite accurate at stoichiometric composition, it appears to do less well in the more general case. The tetrahedral approximation of the cluster variation method predicts a topology of the phase diagram, in the case of nearest neighbor interaction different from the computer simulations. Some consequences for the interpretation of the behavior of copper-gold alloys are indicated.

Al基2元合金の凝固遷移層による流動性，強度形成および割れ感受性の解析

The solid-liquid coexisting zone was classified into the q and the p zone by the fluidity of the liquid between solids. In the q zone having the range of mass fractions of solid of 0 to 0.67, the liquid between the solids can flow, and in the p zone, which has the range of 0.67 to 1.0, the liquid is entrapped by the solids and cannot flow through the solids. The solidification ranges of the q and the p zones were evaluated by the diffusion-controlled equation introducing the term of the mean solute concentration in solid and are shown in the equilibrium phase diagram of an Al-base binary alloy. The flow length in the fluidity test of binary alloys was corresponding to the reciprocal of the solidification range of the q zone. The strength during solidification originated at a mass fraction of solid of 0.67 on the boundary between the q and the p zones, increased with increasing fraction of solid and rapidly increased at the end of solidification. The crack length in the ring test of binary alloys increased with the width of the primary crystallization in the p zone and the fraction of volume contraction in its zone.

Phase diagrams of ascending and minimum type in terms of concentration fluctuations in binary liquid and solid solutions

Abstract The thermodynamics of binary alloy phase diagrams of ascending and minimum types is shown to lead to a rather direct relation between the ratio of the slopes of the liquidus and the solidus curves, at a given temperature T, and the ratio <(δc)2 1(δc)2 s of the concentration fluctuations in the liquid and the solid solutions. The latent heats of the two pure components also enter in a direct manner, as could have been anticipated from the results of ideal solution theory

Short range order and phase diagrams of binary alloys

The form of the liquidus and solidus curves of a binary alloy is shown to be dominated by the concentration fluctuations in the liquid alloy and the short range ordering in the solid solution. Results are reported for Au-Cu.

The electronic structure and phase diagrams of binary alloys with complex lattices: II. MgCd System

AbstractA general theory given in a previous paper which allows to determine theoretically the structures of ordered phases in binary alloys with complex lattice is used for an investigation of the system MgCd. The equilibrium value of the lattice parameter a in the disordered solution is calculated as a function of concentration. For a definite model potential the energetically favoured superstructures are obtained and compared with those observed experimentally.

The electronic structure and phase diagrams of binary alloys with complex lattices: I. The application of static concentration waves and pseudopotential methods for calculating the phase diagrams

AbstractIt is shown that the structures of the ordered phases in binary alloys with complex Ising lattice (made up by the α‐Bravais lattices displaced with respect to each other) can be determined theoretically by means of the static concentration wave (s.c.w.) method and pseudopotential theory. The expression which gives the relationship between the phenomenological parameters of the s.c.w. method and the energy‐wavenumber characteristicof thepseudopotential theory is obtained. The superstructures which may be stable with respect to the formation of an antiphase boundary structure is obtained for the hexagonal close‐packed lattice.

Primary solid solutions in binary nickel alloy systems

The alloying behavior of 40 binary nickel alloy systems was studied in order to determine the extent to which the Hume-Rothery alloying rules apply. An attempt was made to utilize computer facilities in seeking trends of systematic relationships among the various nickel alloys. The nickel-rich parts of the binary-alloy phase diagrams were considered.

Variation of Magnetic Moment with Composition in the Iron-Vanadium Sigma Phase

SINCE the structure of the sigma phase was established by Bergman and Shoemaker1, it has been found in many binary alloys of transition elements (see, for example, Haworth and Hume-Rothery2). Where the phase boundaries have been established, the width of the range of composition varies from less than 1 per cent in the molybdenum–cobalt system to about 20 per cent in the iron-vanadium system. On the basis of the positions of the phase in various binary alloy phase diagrams, it has been suggested that the sigma phase is some kind of electron compound (see, for example, Kasper3). Greenfield and Beck4 concluded that while the sigma phase might be associated with a particular average number of vacancies in electronic ‘d’ states per atom, no self-consistent scheme could be developed to reconcile both theory and experiment. Nevertheless, the possibility that ‘d’ state vacancies might play a part in stabilizing the structure suggests that magnetic evidence would prove of value. Consequently, in a survey of many binary and ternary sigma phase alloys, Nevitt and Beck5 concluded that all were ferromagnetic, having Curie points in the temperature range 50–200° K. No measurements had been made, however, of the mean magnetic moment per atom (PB) of any ferromagnetic sigma phase, or of its variation, if any, with composition, and so the present work was undertaken, the iron-vanadium system being chosen because of the comparatively wide range of composition over which the sigma phase extends.