Intrinsic diffusion and vacancy wind effects in Ag-Cd alloys

Correlation between estimated diffusion coefficients from different types of diffusion couples in multicomponent system

Diffusion studies were made in the alpha and beta phases of the silver-zinc system at 600°C with vapor-solid and solid-solid diffusion couples in order to determine intrinsic diffusion coefficients and interdiffusion coefficients. Intrinsic diffusion coefficients, DZn and DAg, determined experimentally for bothα andβ alloys, were compared with those predicted from the models of Darken, Manning, and Dayananda with the aid of thermodynamic and single crystal tracer diffusion data. The experimental values of Dzn were close to those predicted by the models of Darken and Manning, while the experimental DAg values were higher than those determined by both models. The experimental values of the ratio, DZn/DAg, were found to be lower than those predicted by either Darken’s or Manning’s relations. Also, Dayananda’s model was found to be inapplicable with the available tracer diffusion data. This disagreement is considered to reflect the inadequacy of the single crystal tracer diffusivities in the analysis of intrinsic diffusion in polycrystalline Ag-Zn alloys.

The effect of large vacancy concentration on intrinsic and interdiffusion coefficients: A first-principle study of B2-NiAl

Study of diffusion and atomic mobilities for fcc Ag–Cd and Ag–Sn solder alloys

On the determination of diffusion coefficients in multi-phase ternary couples

Abstract

Diffusion simulation based on atomistic model and mobility determination via Kirkendall experiment for multi-component systems

First discovered by the late Dr John Manning, the vacancy-wind effect is a subtle phenomenon that occurs when two or more atomic species compete for vacancies in a net vacancy flux. The vacancy-wind effect is incorporated in (for example) the vacancy-wind or Manning factor that appears in the Darken-Manning Equation relating the interdiffusivity, the tracer diffusivities and the thermodynamic factor. The mechanism of the vacancy-wind phenomenon has long been very poorly understood. Recently, a moving reference frame Monte Carlo method was used to illustrate graphically how the vacancy-wind effect operates in both ionic conductivity in an ionic solid with a dilute solute and chemical interdiffusion in concentrated alloys and ionic compounds. That strategy is extended in this paper to show graphically how the vacancy-wind effect operates in interdiffusion in a stoichiometric intermetallic taking the B2 structure. A simple 4-frequency vacancy diffusion model is used. In previous work, it was shown that depending on composition and temperature, this model can exhibit the six-jump-cycle mechanism. It is shown that in the limit of perfect order that there is no vacancy-wind effect associated with this mechanism when both types of cycle operate equally (zero net vacancy flux). The non-unity value of the vacancy-wind factor found for this mechanism under zero vacancy flux conditions is purely a consequence of a particular geometric mix of tracer and collective atom displacements. The concept that a non-zero off-diagonal phenomenological coefficient provides the vacancy-wind effect is verified.

Interdiffusion coefficients in copper-rich copper-antimony solid solutions containing up to 5 at% of Sb have been determined by Matano’s method in the temperature range between 919 and 1040 K using semi-infinite diffusion couples consisting of pure copper and Cu–Sb alloys with the Kirkendall markers. From the interdiffusion coefficient and the marker shift, the intrinsic diffusion coefficients have been determined at the marker positions, 1.0 and 1.7 at%Sb. Using thin plate couples, the intrinsic diffusion coefficients in Cu-0.6 at%Sb alloy at 1005 K have been determined by Heumann’s method. From the value of the intrinsic diffusion coefficient of copper in the infinite dilution of Sb and the tracer diffusion coefficients of Sb and Cu in pure Cu, the vacancy flow factor for the interdiffusion in Cu–Sb alloys at 1005 K has been calculated to be −1.20−0.28+0.22, which suggests a strong interaction between an antimony atom and a vacancy. Combining the present result on the vacancy flow factor with the previous experimental data on the enhancement factor of solvent diffusivity by the addition of solute atoms, the correlation factor and the jump frequency ratios in the five-frequency model have been estimated. The correlation factor for the impurity diffusion of Sb in Cu thus obtained is about 0.1 at 1005 K, which indicates highly correlated jumps of an antimony atom to a vacancy.

New method for measurement of interdiffusion coefficient in high temperature solutions based on Fick's first law

One of the Darken equationsgives a relationship between the intrinsic and the tracer diffusion coefficients, D_{A} and D_{A}^{*}, of species A in a solid binary mixture. In its original formulation, the equationreads D_{A}=D_{A}^{*}Γ, with Γ the thermodynamic factor. The question addressed in this paper is how D_{A} and D_{A}^{*} depend separately on Γ. Using a recent result for transition probabilities in terms of the excess chemical potential [M. Di Muro and M. Hoyuelos, Phys. Rev. E 104, 044104 (2021)2470-004510.1103/PhysRevE.104.044104], it is shown that the intrinsic diffusivity does not depend on Γ. This approach simplifies a previous theoretical analysis that reaches the same result. Experimental results of diffusion in Ni-Pd and Fe-Pd alloys [M. J. H. van Dal et al., Acta Mater. 48, 385 (2000)1359-645410.1016/S1359-6454(99)00375-4] are used to check the theory. Numerical simulations of Ni-Pd were performed to show that the migration energy is the main factor responsible for the increase in diffusivity at intermediate concentrations.

A THEORY OF DIFFUSION IN THE L12 STRUCTURE II: TRACER AND CHEMICAL DIFFUSION

Atomic mobility, diffusivity and diffusion growth simulation for fcc Cu–Mn–Ni alloys

Diffusion in ordered alloys and intermetallic compounds

On diffusion in the β-NiAl phase