Изучение ГЦК-ОЦК фазового перехода в сплаве Au-Fe

The properties of the disordered Au-Fe substitution alloy are studied based on the analytical method, which uses the paired interatomic potential of Mie–Lennard-Jones. The parameters of the interatomic potential for the FCC and BCC structures of Au and Fe are determined. Based on these parameters, the concentration dependences of the properties of the FCC and BCC structures of the Au-Fe alloy are calculated. Under normal conditions (i.e., pressure P = 0 and temperature T = 300 K), changes in the properties of the Au-Fe alloy at the structural phase transition of FCC-BCC are calculated. Using the RP-model of the nanocrystal, the displacement of the Cf concentration, at which the FCC-BCC phase transition occurs, due to a decrease in the size of the nanoparticle was calculated. It is shown that at an isochoric-isothermal decrease in the number of atoms (N) in an Au-Fe nanoparticle, the Cf value displace towards higher Fe concentrations. For a nanoparticle with a fixed number of atoms and a constant surface shape, the Cf value increases at an isochoric increase in temperature, and the Cf value decreases at an isothermal decrease in density. Calculations have shown that at N < 59900 for the Au1–CFeC alloy at P = 0, T < 300 K and at any iron concentration, the FCC structure is more stable than the BCC structure.

THE SIZE DEPENDENCIES OF PROPERTIES OF MO-W ALLOY OF EQUIATOMIC COMPOSITION

Основываясь на параметрах парного потенциала межатомного взаимодействия Ми-Леннард-Джонса для Mo и W были рассчитаны параметры потенциала для сплава замещения Mo - W эквиатомного состава. Получены размерные зависимости для уравнения состояния, модуля упругости, коэффициента теплового расширения, изобарной теплоемкости, поверхностной энергии и производной поверхностной энергии по температуре. Также получены температурные зависимости коэффициента теплового расширения изобарной теплоемкости для макро- и нанокристаллов сплава Mo - W. Было показано, что температурная зависимость коэффициента теплового объемного расширения для нанокристалла лежит выше, чем зависимость для макрокристалла, также обнаружено, что с уменьшением размера уменьшается модуль упругости, коэффициент теплового объемного расширения возрастает, а удельная поверхностная энергия нанокристалла сплава Mo - W уменьшается. Based on the parameters of the Mie-Lennard-Jones pair-wised potential of the interatomic interaction for Mo and W , the potential parameters for an equiatomic Mo - W substitution alloy were calculated. Size dependences for the equation of state, modulus of elasticity, coefficient of thermal expansion, isobaric heat capacity, surface energy and surface energy temperature derivative were obtained. Temperature dependencies of coefficient of thermal expansion and isobaric heat capacity for macro- and nano-crystals of Mo - W alloy were also obtained. It was shown that the temperature dependence of the thermal expansion coefficient for a nanocrystal is higher than that for a macrocrystal. It was also found that with a decrease in size, the elastic modulus decreases, the thermal volume expansion coefficient increases, and the specific surface energy of the alloy nanocrystal Mo - W decreases.

Изучение свойств сплава золото-железо в макро- и нанокристаллических состояниях в различных P-T-условиях

For a disordered fcc-Au-Fe substitution alloy, the parameters of the Mie–Lennard-Jones pairwise interatomic potential are determined. Based on these parameters, the concentration dependencies of lattice properties for the macrocrystal of this alloy are calculated. Calculations of 20 properties of macrocrystals fcc-Au, fcc-Fe and fcc-Au0.5Fe0.5 are showed good agreement with experimental data. Using the RP-model of the nanocrystal, the state equation P(v, T; N) and baric dependences of both lattice and surface properties of the fcc-Au0.5Fe0.5 alloy are calculated. Calculations were performed at temperatures T = 100, 300 and 500 K for both a macrocrystal (N = Macro) and a cubic nanocrystal with N = 306 atoms. It is shown that with an isothermal-isobaric (P = 0) decrease in the size of a nanocrystal, its the Debye temperature, elastic modulus, and specific surface energy decrease, while its the specific volume, thermal expansion coefficient, specific heat capacity, and Poisson's ratio increase. At low temperatures in a certain pressure region, the specific surface energy increases at an isothermal-isobaric decrease in the number of atoms in the nanocrystal. As the temperature increases, this pressure region disappears.

Elastic Moduli and Elastic Constants of Alloy AuCuSi With FCC Structure Under Pressure

This paper studies on the dependence of the mean nearest neighbor distance, the Young modulus E, the bulk modulus K, the rigidity modulus G and the elastic constants C11, C12, C44 on temperature, pressure, the concentration of substitution atoms and the concentration of interstitial atoms for alloy AuCuSi (substitution alloy AuCu with interstitial atom Si) with FCC structure by the way of the statistical moment method (SMM). The numerical results for alloy AuCuSi are compared with the numerical results for main metal Au, substitution alloy AuCu, interstitial alloy AuSi, other calculated results and experiments.

Studying the Effects of Vacancies on the Melting Temperature of \(\text{AgCe}\) Alloy

In order to evaluate the effects of vacancies on the melting temperature of AgCe alloy, the statistical moment method was used to find out the analytical expressions to determine the Gibbs free energy in the AB substitution alloy and the expression to calculate the melting temperature of perfect and imperfect AB substitution Alloys. The melting temperature was calculated by the numerical calculation method on the perfect and imperfect AgCe alloy. The calculating results shown that the melting temperature of alloys increase with a increase in pressure. The melting temperatures of imperfect alloy of AgCe, Ag2Ce and Ag3Ce are always slightly lower than that of perfect alloys. Especially, the melting temperatures value of perfect and imperfect alloy were almost the same at high pressure. The melting temperature of alloys increase with an increase in amount of Ag containing in the alloys. The calculated results agreed well with the experimental results at P = 0.

О вычислении температуры Дебая и температуры фазового перехода кристалл-жидкость для бинарного сплава замещения

A method of estimating the interatomic pair interaction potential parameters for a binary substitution alloy with consideration for the deviation of its lattice parameter from the Vegard law is proposed. This method is used as a basis to calculate the Debye temperature and Grüneisen parameters of a SiGe alloy. It is shown that all these function nonlinearly variate with a change in the germanium concentration. Based on this technique and Lindemann's melting criterion, a method for calculating the liquidus and solidus temperatures of a disordered substitution alloy is proposed. The method is tested on the SiGe alloy and demonstrates good agreement with experimental data. It is shown that when the size of a nanocrystal of a solid substitution solution decreases, the difference between the liquidus and solidus temperatures decreases the more, the more noticeably the nanocrystal shape is deflected from the most energetically optimal shape.