scholarly journals Interdiffusion Data in Multicomponent Alloys as a Source of Quantitative Fundamental Diffusion Information

2007 ◽  
Vol 263 ◽  
pp. 1-10 ◽  
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Diffusion Processes ◽  
Chemical Diffusion ◽  
Tracer Diffusion ◽  
Ternary Alloys ◽  
Diffusion Data ◽  
Fundamental Information ◽  
Random Alloy ◽  
Phenomenological Coefficients ◽  
Correlation Factors ◽  
Alloy Systems

Tracer diffusion experiments have historically furnished much of the information about fundamental diffusion processes as embodied in such quantities as tracer correlation factors and vacancy-atom exchange frequencies. As tracer diffusion experiments using radiotracers are rather less often performed nowadays, it is important to be able to process other diffusion data to provide similar fundamental information. New procedures that are primarily based around the random alloy model have been established recently for analyzing chemical diffusion data in binary and ternary alloy systems. These procedures are reviewed here. First, we review the random alloy model, the Sum-rule relating the phenomenological coefficients and three diffusion kinetics formalisms making use of the random alloy. Next, we show how atom-vacancy exchange frequency ratios and then component tracer correlation factors can be extracted from chemical diffusion data in alloy systems. Examples are taken from intrinsic diffusion and interdiffusion data in a number of binary and ternary alloys.

scholarly journals Analysis of Interdiffusion and Intrinsic Diffusion in Multicomponent Alloys to Obtain Information about Diffusion Mechanisms

2006 ◽  
Vol 258-260 ◽  
pp. 237-246
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Chemical Diffusion ◽  
Tracer Diffusion ◽  
Intrinsic Diffusion ◽  
Diffusion Data ◽  
Ternary Alloy Systems ◽  
Ni Alloy ◽  
Diffusion Mechanisms ◽  
Correlation Factors ◽  
Tracer Diffusion Data ◽  
Alloy Systems

In this paper, we present and discuss some of the theoretical procedures that have been established recently for binary and ternary alloy systems for the purposes of analyzing chemical diffusion data (interdiffusion and intrinsic diffusion) alone and chemical diffusion data in combination with tracer diffusion data. Emphasis is put on extracting information about diffusion mechanisms by way of tracer correlation factors/vacancy-wind factors. Examples are taken from the intrinsic diffusion, interdiffusion and tracer diffusion data in the Ag-Cd and Ag-Cd-Zn, Fe-Ni-Cr and Cu-Fe-Ni alloy systems.

Correlation Effects and Activation Energies for Diffusion in Alloys

1971 ◽  
Vol 26 (1) ◽  
pp. 69-76 ◽  
Author(s):  
John R. Manning
Keyword(s):  
Temperature Dependence ◽  
Analytic Form ◽  
Activation Energies ◽  
Tracer Diffusion ◽  
Correlation Factor ◽  
Face Centered Cubic ◽  
Random Alloy ◽  
The Difference ◽  
Jump Frequencies ◽  
Correlation Factors

Abstract The problems involved in calculating correlation factors for diffusion in dilute alloys can be contrasted to those arising in concentrated solid solutions. As one moves from the pure element to the dilute alloy to the concentrated alloy, the calculation becomes progressively more difficult. Because of the complex atom configurations which can occur in concentrated alloys, it usually is not possible to calculate correlation factors in these alloys exactly. Several important simplifications are available in non-dilute random alloys. A large reduction in complexity can be secured by using a random alloy model where each atom is treated as diffusing in a uniform matrix, with the matrix properties being determined by the composition and jump frequencies in the alloy. Resulting equations in this random alloy model can be expressed directly in terms of the experimentally measurable tracer diffusion coefficients with no unknown vacancy jump frequencies appearing. Also these equations have the advantage of being in simple analytic form and not requiring numerical methods to evaluate the correlation factors. These two features make possible the direct expression of the temperature dependence of the correlation factor in terms of the experimental activation energies.Equations are found for ΔH/ΔQ in random binary cubic alloys, where AH is the difference between the activation enthalpies for diffusion of the two species and ΔQ is the difference between the experimentally measured activation energies of the two species. This ratio is never less than unity and can be much larger than unity. Values are plotted for diamond, body-centered cubic and face-centered cubic structures. From the magnitude and composition dependence of ΔH/ΔQ, it is concluded that the temperature dependence of the correlation factor cannot by itself explain the difference between the activation energies measured from tracer diffusion and from internal friction in the non-dilute range

Diffusion in Materials with Ionic and Electronic Disorder

1990 ◽  
Vol 210 ◽  
Author(s):  
Joachim Maier
Keyword(s):  
Ionic Conduction ◽  
Diffusion Theory ◽  
Local Equilibrium ◽  
Transport Coefficients ◽  
Electrochemical Techniques ◽  
Chemical Diffusion ◽  
Tracer Diffusion ◽  
Internal Defect ◽  
Concentration Cell ◽  
The Individual

AbstractBesides some necessary reviewing of conventional diffusion theory, this paper deals with the modification of the mass and charge transport equations originating from the occurence of internal defect-chemical reactions (especially valence changes of the defects) which can be considered to be in local equilibrium. It is shown how the phenomenological transport coefficients for chemical diffusion, tracer diffusion and ionic conduction depend on the individual defect diffusivities under such general conditions. Moreover, the evaluation formulae of well-known electrochemical techniques such as Wagner-Hebb polarization and concentration cell experiments have to be modified. Application is made to the influence of trapping effects in doped SrTi03, to the valence changes in YBa2Cu3O6+x as well as to the mixed conduction in orthorhombic PbO.

High-Temperature Oxidation of Stainless Steels

MRS Bulletin ◽  
1994 ◽  
Vol 19 (10) ◽  
pp. 23-25 ◽  
Author(s):  
J.C. Colson ◽  
J.P. Larpin
Keyword(s):  
High Temperature ◽  
Stainless Steels ◽  
Diffusion Processes ◽  
Short Circuit ◽  
High Temperature Corrosion ◽  
Corrosion Products ◽  
Ternary Alloys ◽  
Low Carbon ◽  
Scale Growth ◽  
Temperature Oxidation

The first stainless steels, mainly low carbon chromium-iron alloys, have been known since the beginning of this century. These steels show good resistance against wet corrosion and high-temperature corrosion. This article focuses on high-temperature corrosion, with emphasis on gaseous sulfidizing and oxidizing environments. The discussion is limited to these two gases since corrosion involving halogen-and/or carbon-containing gases involves other specific processes. The behavior of binary and ternary alloys will be successively examined, then the role of minor elements will be considered.Fundamental Mechanisms of High-Temperature Corrosion of Stainless SteelUsually, a dry corrosion process results in the formation of corrosion products, giving a simple or complex oxide or sulfide scale on a metallic substrate, separating it from the aggressive gaseous environment and, consequently, acting as a protective barrier. Scale growth is controlled by the conductivity of the reaction products which are solid electrolytes. Generally, the mechanism of scale growth is governed by outward cation or inward anion diffusion processes. This is the basis of the model originally put forward by Wagner for a single metal and subsequently developed for alloys, and particularly, for stainless steels. This one-way point-defect diffusion process is responsible for the observed parabolic scaling kinetics characterized by a parabolic rate constant kp. This model is well described in the literature.In the case of stainless steels, formation of a protective scale is required; this is possible if the oxide or sulfide products have a low diffusivity to cations or anions due to a low density of point defects in the crystal lattice. The protective characteristics of the corrosion products may be experimentally determined by measurement of their electrical conductivity, although the scales should also be effective against short-circuit transport of ions, atoms, or molecules. The best barriers consist of oxides, such as Al2O3, SiO2, and Cr2O3.

Tracer correlation factors in the random alloy

2000 ◽  
Vol 80 (7) ◽  
pp. 1469-1479 ◽  
Author(s):  
I. V. Belova ◽  
G. E. Murch
Keyword(s):  
Random Alloy ◽  
Correlation Factors

Cluster-Based Bulk Metallic Glass Formation in Co (-Fe)-Si-B-Nb Alloy Systems

2007 ◽  
Vol 561-565 ◽  
pp. 1275-1278 ◽  
Author(s):  
Qing Wang ◽  
Chun Lei Zhu ◽  
Yan Hui Li ◽  
Jiang Wu ◽  
Chuang Dong ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Bulk Metallic Glasses ◽  
Ternary Alloys ◽  
Glass Forming ◽  
Binary Clusters ◽  
Composition Formula ◽  
Alloy Systems

The present paper investigates the bulk metallic glass formation in Co-based alloy systems with the guidance of the cluster line and minor-alloying principles. The selected basic ternary Co-B-Si alloy compositions are intersecting points of cluster lines, defined by linking special binary clusters to the third element. Then these basic ternary alloys are further minor-alloyed with Nb and quaternary bulk metallic glasses are obtained only by 4-5 at. % Nb minor-alloying of the basic composition Co68.6B25.7Si5.7 that is developed from dense-packed cluster Co8B3. The bulk metallic glasses are expressed approximately with a unified simple composition formula: (Co8B3)1(Si,Nb)1. In addition, a quantity of Fe substitution for Co further improves the glass-forming abilities.

New developments in thermo-chemical diffusion processes

2005 ◽  
Vol 200 (5-6) ◽  
pp. 1830-1836 ◽  
Author(s):  
Winfried Gräfen ◽  
Bernd Edenhofer
Keyword(s):  
Diffusion Processes ◽  
Chemical Diffusion ◽  
New Developments
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