Vacancy concentration at antiphase boundaries in ternary ordered alloys

A theoretical study is made of the dependence of the vacancy concentration at antiphase boundaries in ternary ordered bcc alloys on the long-range order, the temperature, and the degree to which the atoms of the third (impurity) element interact with atoms of the other species. The theory is applicable to specific types of antiphase boundaries in ternary alloys corresponding to the quasibinary BA-BD section.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 1, pp. 119–124, January, 1970.     

Theory of adsorption at antiphase boundaries in ternary fcc ordered alloys

The adsorption of alloying elements at (111) antiphase boundaries (APB's) in ternary fcc ordered alloys is analyzed. The atomic segregation at the APB's and the long-range order parameters at the APB's and within domains are studied as functions of the temperature and the concentration of alloying elements. The results are compared with experimental data for ternary bcc alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 2, pp. 96–104, February, 1971.     

Relationship between antiphase boundaries and dislocations in ordered alloys

The general close relationship between antiphase boundaries (due to slip, interstitial atoms, or vacancies) and dislocations in ordered alloys which results from the geometry of these defects is demonstrated by the method of Burgers contours. Certain consequences of this relationship affect the dependence of the domain structure of alloys on the original dislocation structure.Reported to the V Intercollegiate All-Union Scientific Conference on the Strength and Plasticity of Metals and Alloys, held July, 1967, in Petrozavodsk.Translated from Izvestiya VUZ. Fizika, No. 3, pp. 108–112, March, 1970.     

Atomic configuration of antiphase boundaries in alloys

Computer simulation methods in the approximation of pairwise interatomic Morse potentials are used to calculate the atomic configurations and the energy of formation of 1/2 <110> {111} antiphase boundaries in ordered Cu₃Au and Ni₃Fe alloys. Atomic displacements result in considerable smearing of the first five planes closest to an antiphase boundary and a slip of atomic planes. These effects substantially reduce the energy of formation of antiphase boundaries. The influence of the size factor on the atomic configuration on the antiphase boundaries is discussed.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 2, pp. 43–47, February, 1985.In conclusion, the authors express their thanks to A. I. Tsaregorodtsev for useful discussion of this work.     

Etching of slip produced antiphase domain boundaries in iron-silicon alloys

A method for revealing the slip produced antiphase domain boundaries in nearly stoichiometric ordered Fe₃Si alloys by chemical etching in a solution of HF + H₂O₂ + H₂O is reported. The method was applied to determine the character of superlattice dislocations in strained crystals. Perfect superlattice dislocations were found at the beginning of deformation. Imperfect superlattice dislocations producing antiphase domain boundaries were found at higher deformations.     

Metastable states in ternary ordered alloys

The Gorskii-Bragg-Williams approximation is employed in a theoretical study of certain features in the atomic distribution in ternary ordered alloys having fcc lattices. The effect of various parameters in the interatomic interactions and of the concentration of the third alloying element are studied for their influence on the formation of metastable states in these alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 31–34, June, 1971.     

Segregation of impurities and vacancies on phase and antiphase boundaries in alloys

The equilibrium distribution of low-concentration impurities or vacancies is investigated in the region of a coherent phase boundary or antiphase boundary in a binary alloy. A general expression for the free energy of an inhomogeneous multicomponent alloy, which generalizes the expression previously derived for a binary alloy, is presented. Explicit formulas for the impurity concentration profile c _im(x) in terms of the distribution of the principal components of the alloy near a boundary are obtained from this expression in the mean-field and pair-cluster approximations. The shape of this profile is determined by a “preference potential” P, which characterizes the attraction of an impurity to one of the alloy components, as well as by the temperature T and the phase transition temperature T c. At small values of P/T impurities segregate on a phase boundary, and the degree of this segregation, i.e, the height of the maximum of c _im(x), in the region of the boundary increases exponentially as the ratio T _c/T increases. For P ≠ 0 the c _im(x) profile near a phase boundary is asymmetric, and as P/T increases, it takes on the form of a “worn step.” The maximum on the c _im(x) curve then decreases, and at a certain |P|≳T _c it vanishes. Segregation on an antiphase boundary is investigated in the case of CuZn ordering in a bcc alloy. The form of c _im(x) near an antiphase boundary depends significantly both on the form of the potential P and on the stoichiometry of the alloy. At small P impurities segregate on an antiphase boundary, and at fairly large P “antisegregation,” i.e., a decrease in the impurity concentration on the antiphase boundary in comparison with the value within the antiphase domains, is also possible. Zh. éksp. Teor. Fiz. 112, 714–728 (August 1997)     

The lattice deformation and the energy of antiphase boundaries in Fe-Si alloys

The lattice deformation across the antiphase boundary and the energy of both types (a/2111 anda(100) of antiphase boundaries lying in {110} plane are calculated using a series of three interatomic potentials fitted to experimental data. It is shown that the relaxation of atomic planes in the vicinity of antiphase boundary is important for thea/2111 antiphase boundary and is negligible for a 100 antiphase boundary in the DO₃ structure.The author is grateful to Dr. F.Kroupa and to Dr. A.Gemperle for valuable discussions.     

Influence of antiphase domain boundaries on the formation of magnetic order in alloys

We consider the influence of boundaries between structural domains on the atomic and magnetic order in substitutional binary alloys. We calculate the variation of the composition at antiphase boundaries. We show that when the magnetic phase transition temperature of the alloy is below the Kurnakov point, the development of magnetic order at the boundaries may begin at higher temperatures than within the domains. It is then possible that the type of magnetic order at the boundaries may change (ferromagnetic into antiferromagnetic, or vice-versa) when magnetic order appears within the domains.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 13–17, August, 1991.     

The theory of equilibrium antiphase boundaries in ordered solid solutions of the AuCu3 type

The Gorsky-Bragg-Williams approximation gives expressions which determine the equilibrium values of the long-range-order parameter and the concentrations of components in the vicinity of the antiphase boundary 1/2 (110) {111} in an L1₂ super-structure of stoichiometric composition AB₃. On the assumption that the changes in the alloy due to the presence of an antiphase boundary are distributed over a great number of planes on both sides of the boundary, the long-range-order parameter and the concentration of components in these planes have been calculated. It is found that the long-range-order parameter at the antiphase boundary is considerably lower than it is in the matrix over a wide temperature range. The concentration of the components at the antiphase boundary under conditions of thermodynamic equilibrium is somewhat lower than the mean concentration in the alloy.Estimates are made of the critical stress for the start of superdislocations with equilibrium antiphase boundaries, the equilibrium width of the superdislocations, and the defect in the elastic modulus due to the reversible movement of the superparticle dislocations.     

Segregations at antiphase boundaries in hexagonal close-packed superstructures. II

As was shown in the first part of this study [1], slip occurs in polycrystalline ordered Mg₃Cd, which has a DO₁₉ superstructure, along the {0001} basis planes, {1010} prismatic planes, and {1011} and {1012} pyramidal planes [2,3]. The formation of segregations at antiphase boundaries (APB's) in the {0001} basis and {1011} pyramidal planes was also examined there [1]. Segregations at APB's in planes are treated in this second part of the study. A zero-energy APB may form in the prismatic plane [4]. Segregation of atoms, on the other hand, is not allowed at such an APB according to the Gorskii-Bragg-Williams theory if correlation and interaction in the second and higher coordination spheres are not taken into account.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 5, pp. 62–70, May, 1969.The authors thank N. S. Golosov and N. V. Kozhemyakin for discussion of this study and valuable advice.