Abstract
A non-isothermal method for the determination of the gas diffusivity in metals and alloys is proposed. The method allows to determine the temperature dependence of the gas diffusion coefficient in a wide temperature range with a limited number of experiments. The results obtained with this method (for the diffusivity of nitrogen in steels), agree favourably with the diffusion data obtained with other experimental techniques. Hence, the proposed method leads to reliable results and can be successfully used in further studies.
Abstract
Hiermit wird eine nichtisotherme Methode zur Bestimmung von Gasdiffusionskoeffizienten in Metallen vorgestellt, mit deren Hilfe die Temperaturabhängigkeit des Koeffizienten in einem weiten Temperaturbereich über eine geringe Zahl von Experimenten bestimmt werden kann.
Die auf diese Weise erhaltenen Ergebnisse über die Diffusion von Stickstoff in Stählen stimmen sehr gut mit den Daten, welche bis jetzt anhand anderer experimenteller Techniken ermittelt worden sind, überein.
Es ist festzustellen, daß die vorgestellte Methode zuverlässig genug ist, um zu weiteren Untersuchungen zur Bestimmung des Gasdiffusionskoeffizienten in Metallen herangezogen werden zu können.
The authors are grateful to the Volkswagen Stiftung for the financial support of the present research. We also wish to thank Prof. J. Sietsma (Delft University, Netherlands) and Dr. K. Russew (IMS, Sofia) for the kindly given FORTRAN-version of the Nelder-Mead simplex algorithm.
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Appendix
Error analysis
Let us consider Eq. (9) taking into account, that the values of Tm, I and α are measured with definite accuracy ∆Tm, ∆I and ∆α. Therefore, instead Tm, I and α, the values of these quantities substituted into Eq. (9) are Tm = Tm ± ΔTm, I = I ± ΔI and α = α ± Δα (Note that our analysis assumes ΔTm/Tm ≪ 1, ΔI/I ≪ 1 and Δα/α ≪ 1:
Rearranging the members of the left and the right hand side of the Eq. (A1) it is obtained:
In the above equation it is accounted for that the errors of the measurements has a cumulative effect on the final result. That is why, in the second and the fourth members of Eq. (A2) instead (∓) appears (±) operation. Taking into account this circumstance and that for x ≪ 1 – ln(1 ± x)≈ ±x, the above equation yields:
Here
Finally the above equation can be rewritten as follows:
where
© 1998 Carl Hanser Verlag, München
Artikel in diesem Heft
- Frontmatter
- Aufsätze
- Study of the Transitions AuCu I → AuCu II → Disorder by Differential Scanning Calorimetry
- Critical Data and Vapor Pressures for Aluminium and Copper
- Study of Al1–xTixB2 Particles Extracted from Al–Ti–B Alloys
- Experimental Investigation and Thermodynamic Modeling of the Ni–Ti–C System
- Erratum
- Determination of the Nitrogen Diffusion Coefficient in Steels with Non-isothermal Experiments
- Microstructures and Hot Tensile Properties of Pressure-diecast and Gravity-cast Commercial Zinc-based Alloys
- Development of Annealing Textures in Al–Mg Alloys
- Hot Deformation and Microstructural Evolution in an α2/O Titanium Aluminide Alloy Ti-25Al-15Nb
- Microhardness of Structure Units in the Ternary Ti-rich Ti–Si–Al Alloys
- Metallurgical Factors Affecting Impact Toughness of Eutectic Al-Si Casting Alloy
- Mitteilungen der Deutschen Gesellschaft für Materialkunde e.V.
- Personen
- Buchbesprechungen
Artikel in diesem Heft
- Frontmatter
- Aufsätze
- Study of the Transitions AuCu I → AuCu II → Disorder by Differential Scanning Calorimetry
- Critical Data and Vapor Pressures for Aluminium and Copper
- Study of Al1–xTixB2 Particles Extracted from Al–Ti–B Alloys
- Experimental Investigation and Thermodynamic Modeling of the Ni–Ti–C System
- Erratum
- Determination of the Nitrogen Diffusion Coefficient in Steels with Non-isothermal Experiments
- Microstructures and Hot Tensile Properties of Pressure-diecast and Gravity-cast Commercial Zinc-based Alloys
- Development of Annealing Textures in Al–Mg Alloys
- Hot Deformation and Microstructural Evolution in an α2/O Titanium Aluminide Alloy Ti-25Al-15Nb
- Microhardness of Structure Units in the Ternary Ti-rich Ti–Si–Al Alloys
- Metallurgical Factors Affecting Impact Toughness of Eutectic Al-Si Casting Alloy
- Mitteilungen der Deutschen Gesellschaft für Materialkunde e.V.
- Personen
- Buchbesprechungen