Papers by Keyword: Binary Alloy

Abstract: An algorithm is proposed for constructing curves of thermal cooling and ordering kinetics with a monotonic decrease in temperature for alloys to stoichiometric composition. Modeling is carried out by the Monte Carlo method in the model of a rigid crystal lattice and pair interatomic interactions. The application of the algorithm is illustrated by the example to a square lattice, taking into account interatomic interactions in the first two coordination spheres for alloys with the composition AB, A3B, and A3B5. The proposed model makes it possible to calculate individual sections of the phase diagrams to the state for binary alloys.

Abstract: The self-or tracer diffusivity of one component in a binary alloy is often required when there is knowledge of the other component’s self-or tracer diffusivity and the interdiffusivity (and the thermodynamic factor). In the present paper, this problem is addressed for the random alloy model by applying three possible approximations having different levels of accuracy: Darken (low level of accuracy), Manning (medium level of accuracy) and Moleko, Allnatt and Allnatt (MAA) (high level of accuracy). There are unexpectedly large differences between the results of these approximations that sometimes are reflected in the high sensitivity of the vacancy-wind factor to the level of approximation. Generally, for the application of Manning and the MAA approximations, it is found that there is a difference in the number of self-diffusivity roots depending on whether the tracer diffusivity is available for the faster diffuser or for the slower diffuser and depending on how close the composition is to the forbidden (according to Manning’s description) region. Provided that the interdiffusion coefficient (divided by the thermodynamic factor) is greater than the available self-diffusion coefficient multiplied by its complementary composition, the application of the Darken approximation always results in one self-diffusivity root.

Abstract: Theoretical description of ultrathin ferromagnetic Fe and Ni alloy film adsorption on a nonmagnetic metal substrate is considered by the spin-density functional method. The conditions for the formation of ultrathin ferromagnetic films stable with respect to island adsorption with a change in the coverage parameter θ and Fe content concentration x are revealed. The equilibrium vacuum gap D_min and the equilibrium film thickness h_min are determined from the minimum of the total interfacial energy. The energy and magnetic characteristics of Fe_xNi_1-x films on close-packed W and Cu surfaces are calculated in dependence on concentration x for different temperatures.

Abstract: In order to study the growth process and morphology of dendrite directly, a phase field model of binary alloy was established. In this model the order parameter equation was coupled with the temperature field and the solute field. The growing processes and morphology of dendrite were simulated by using this phase field model. Through analyzing the results, we discussed the effects of anisotropic strength and temperature gradient on dendrite morphology. The results shows that with the increasing of anisotropic strength, the dendrite growth rate of the dendrite will increase and the secondary branches appear more clearly. Besides, the temperature gradient has influence on the appearance of secondary arms during the dendrite growing. With the increase of temperature gradient, the size of secondary dendrite arms increase.

Abstract: Electrolytic deposit of indium, platinum and platinum-indium alloy on the surface of graphite electrodes has been studied using the scanning electron microscopy and the stripping voltammetry. The scanning electron microscopy method has revealed that platinum-indium alloy on the surface of the graphite electrode contains indium, platinum and chlorine. But platinum is unable to be determined on the surface of the graphite electrode without a metal activator due to its precipitation in very small quantities. Under the anodic oxidation of indium-platinum precipitation, the anodic peaks caused by the selective electro-oxidation of indium from the intermetallic compounds with platinum are observed on the current-voltage curves. Wherein, platinum remains on the electrode surface, and can be oxidized from the electrode at the potentials of the electrode purification (more than 1 V).

Abstract: Diffraction intensities of a single crystal of Fe₃Pt alloy have been measured by using white X-rays of synchrotron radiation. The observed intensities have been compared with the calculated ones for fundamental and superlattice reflections. By normalizing the calculated intensities of fundamental reflections to the observed ones and evaluating the ratio of the observed intensity of superlattice reflection to the calculated ones, we have estimated the order parameter as 0.82±0.03. The obtained order parameter has been applied to an analysis of the X-ray magnetic diffraction data to estimate the spin moment of Fe and Pt atoms in this alloy.

Abstract: This work investigated the competition effect between the ferro-and antiferro-interaction on the domain size and domain interface in two-dimensional binary alloy. Monte Carlo simulation and Ising model were used to model the alloy system where largest domain size and the domain interface were observed to identify the low temperature ordered phase and the high temperature disordered phase. The simulation results show that domain size is maximized when the ferro-interaction is preferred, but domain interface becomes maximum instead when the antiferro-interaction is favored. These domain properties were reported as a function of temperature for various magnitude of ferro-and antiferro-interactions. In addition, the artificial neural network was used to create database of relationship among the ferro-and antiferro-interaction, the simulated temperature and the domain properties. Good agreement between the real targeted outputs and the predicted outputs was found, which confirm the learning-by-example ability of the artificial neural network. This work therefore presents another step in the understanding of how complex interaction plays its role in binary alloy problem and how a data mining technique assists development of understanding in materials science problems.

Abstract: We have performed X-ray magnetic diffraction experiments of a ferromagnetic binary alloy Fe₃Pt in order phase, and have measured separately spin and orbital magnetic form factors. By a curve-fitting analysis in which atomic-model form factors of Fe-3d and Pt-5d electrons under the dipole approximation are assumed, we have obtained the spin and orbital magnetic moments of Fe and Pt atoms separately. The present result is comparable to those of other experimental and theoretical studies, which shows the validity of this experimental method.

Abstract: A phase-field approach which incorporates mass and momentum and solute conservation equations for simulation of Al-Si binary alloy solidification is studied. The effect of force flow on the dendrite growth and solute profile during the solidification of binary alloy were investigated. The results indicate that dendritic grows unsymmetrically under a forced flow, the growth velocity of the upstream tip is faster than the downstream tip. With the force flow, the upstream tip grows faster due the thinner solute boundary layer. The solute gradient in the solid/liquid interface regions of the upstream tip is higher than that of the downstream tip. The faster the flow velocity, the greater the solute gradients in the solid/liquid interface regions of the upstream tip, the thinner the diffusion layer before the upstream tip. The downstream tip is opposed to the upstream tip. The simulations agree qualitatively with the solidification theoretical results.

Abstract: The results of running a quasi two-dimensional experimental benchmark for horizontal directional solidification of binary Sn-3 wt.%Pb alloy in a rectangular region are presented. The computation was performed using the GIGAN software and two models to simulate the mushy zone were compared, namely, the one based on the equilibrium approach and the non-equilibrium one.