Search

The shift of the Kirkendall marker at the interface of Cu–Ni diffusion couples was examined under the influence of high magnetic fields up to 12 T. The shift distance of the marker increased remarkably with increasing magnetic flux density (B) in the case of the direction of diffusion parallel to B. However, if the direction of the magnetic field was perpendicular to that of diffusion, there was a negligible effect of the magnetic field on diffusion behavior. A calculation of intrinsic diffusivities of both components showed that the interdiffusion rates (∥B) are increased by high magnetic fields. These effects can be attributed to an increase in the chemical potential gradient induced by magnetic free energy in a high magnetic field. [ABSTRACT FROM AUTHOR]

The effects of an 11.5 T high magnetic field on the growth behavior of compounds layers during reactive diffusion in solid Al/solid Mg diffusion couples have been investigated. After annealing with and without a magnetic field, the interfacial zone was still composed of two layers of stable compounds β (MgAl) and γ (MgAl), but the thicknesses of the layers were increased by the magnetic field. Data analysis of the thicknesses of compound layers showed that the growth of the γ layer was controlled by grain boundary diffusion as well as volume diffusion at B=0 T, but only controlled by volume diffusion when an 11.5 T high magnetic field was applied. The interdiffusion coefficients for the samples annealed at 643-693 K were calculated from the parabolic relationship between the migration of the interface and the annealing time. The results show that the diffusion constant increased due to the high magnetic field, increasing the chemical potential gradient, and in turn it caused the interdiffusion coefficient to increase. [ABSTRACT FROM AUTHOR]

The kinetics of the reactive diffusion at the liquid Al/solid Cu interface was investigated at T = 973 K, 1023 K, and 1073 K in a high magnetic field of 11.5 T. During the annealing process, three stable compounds (δ, ξ2, and η2) layers were formed at the interface of the couples, and a power function relationship between the mean thickness of the diffusion layers and the annealing time kept stable. Without magnetic field, the exponent of the power function for each compound layer was higher than 0.5, but it was close to or even smaller than 0.5 with a magnetic field. Compared with the field-free environment, the migration of the liquid/solid interface due to interdiffusion decreased in the presence of a magnetic field. A considerable decrease in the effective diffusion coefficient under a magnetic field provided a likely explanation for the experimental results. [ABSTRACT FROM AUTHOR]

Suitable similarity transformations were used for reducing the generalized N-diffusion equations to a class of singular nonlinear boundary value problems. Similarity solutions are presented analytically and numerically. The results indicated that for each fixed α, the general diffusion flux θ(s) decreases with the increase of the power law N and sharply with the increase of σ. For 0<σ&les;1, θ(s) decrease with the increase of α, however, the behavior is quite opposite for σ>1. [Copyright &y& Elsevier]

Sinter-HIP combining vacuum and pressure in one-step sintering process has been applied to prepare ultrafine crystalline cemented carbide with a surface gradient layer enriched in binder. The effect of powder particle size on gradient formation and grain growth has been examined. The results show that the gradient layer thickness increases with decreasing WC and Ti(C,N) powder particle size. The number of abnormal WC grains increases with decreasing WC powder particle size. The formational mechanism of the gradient cemented carbide with ultrafine grains is discussed through analyzing the decomposability of nanoscale Ti(C,N), atomic diffusion and grain growth during one-step Sinter-HIP process. [ABSTRACT FROM AUTHOR]

Ultrafine crystalline functionally graded cemented carbides (FGCCs) with a surface zone enriched in binder phase were prepared by a one-step Sinter-HIP method. The influence of sintering pressure and cubic carbide composition on the formation of gradient layer was examined. The results show that the ultrafine FGCC with surface zone enriched in binder phase can be formed by the one-step Sinter-HIP method. The process of the gradient layer formation is accelerated under higher sintering pressure; the gradient layer thickness increases with the sintering pressure increasing. The gradient layer thickness is controlled by diffusion distance of cubic carbide formers, such as Ti, Ta and Nb. The addition of (Ta,Nb)C leads to decrease the thickness of gradient layer. [ABSTRACT FROM AUTHOR]

The influence of interdiffusion on the magnetic properties of Co/Si (100) films after thermal annealing in the presence of a strong magnetic field was investigated. The interdiffusion coefficients of films that were annealed at temperatures of 380 °C and 420 °C in the presence of high magnetic fields were not affected. However, the interdiffusion coefficient of films annealed at 400 °C in the presence of a high magnetic field decreased significantly. The change in the interdiffusion coefficient, caused by high magnetic field annealing, increased the content of the magnetic phase. This increase in the magnetic phase improved the saturation magnetization. A new method of high magnetic field annealing is presented that can modulate the diffusion and magnetic properties of thin films. [ABSTRACT FROM AUTHOR]

The effects of high magnetic field annealing on the inter-diffusion behavior of Co/Si (100) films were investigated using diffusion couple technique. Significant Co and Si inter-diffusion was verified by X-ray photoelectron spectroscopy. The inter-diffusion coefficients of thin-film/semiconductor were calculated. Compared to the no-field case, the inter-diffusion coefficients clearly increased when a high magnetic field of 11.5 T was applied at 300 °C, 350 °C, 450 °C and 500 °C. This effect can be attributed to an increase in the chemical potential gradient induced by magnetic free energy in a high magnetic field. For the samples at 400 °C, the inter-diffusion coefficients decreased when a high magnetic field of 11.5 T was applied. The phenomenon may due to the structure transformation caused by a high magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: Isothermal heat treatment experiments of an Al–4.8mass%Cu alloy were carried out under different magnetic field intensities, at different temperatures and for different holding times. The influence of high magnetic fields on area fraction of θ phase in the solidified microstructure was investigated. It was found that the area fraction of the θ phase was lower when imposing the magnetic field compared to samples heat-treated without magnetic field. In other words, the magnetic field accelerated the phase transformation to the equilibrium state. In addition, the area fraction of the θ phase was independent of magnetic field intensity. This effect of high magnetic fields on the decreasing of the θ phase was discussed from the viewpoint of the effect of high magnetic fields on diffusion. [Copyright &y& Elsevier]

Abstract: The effects of high magnetic field annealing on the interdiffusion of Co/Ni bilayer films were investigated in this paper. A clear CoNi alloying zone can be observed by field emission scanning electron microscopy and energy dispersive spectroscopy, for samples annealed with and without magnetic field. Significant Co and Ni interdiffusion was verified by X-ray photoelectron spectroscopy. Based on the thickness of the diffusion layer, the distribution of atoms and the microstructure of interfacial products, the interdiffusion coefficients of the bilayer diffusion couples were calculated. Compared with the no-field case, the interdiffusion coefficient clearly increased when a high magnetic field of 12T was applied. This effect can be attributed to an increase in the chemical potential gradient induced by magnetic free energy in a high magnetic field. [Copyright &y& Elsevier]

Abstract: The application of a high magnetic field during pack aluminization process induced a significant change in the final products at the surface of substrate Cu. Experimental studies demonstrated that the coatings consisted of two layers namely α + γ 2 and α with the magnetic flux density (B) ranging from 0 to 8.8 T, whereas only α layer with Kirkendall voids was observed in case of B ≥10 T. With B increasing, the total thickness of coating first increased to a maximum at a field of 6.6 T, and then decreased with further increasing magnetic flux density. These results may be attributed to the contradictory effects of high magnetic fields on chemical reaction and on diffusion. [Copyright &y& Elsevier]