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Impact of Values of Diffusion Coefficient on Results of Diffusion Modelling Driven by Chemical Potential Gradien

Wróbel Marek, Burbelko Andriy

Archives of Foundry Engineering

2022

Vol. 22, iss. 3

81--90

In the paper critical role of including the right material parameters, as input values for computer modelling, is stressed. The presented model of diffusion, based on chemical potential gradient, in order to perform calculations, requires a parameter called mobility, which can be calculated using the diffusion coefficient. When analysing the diffusion problem, it is a common practice to assume the diffusion coefficient to be a constant within the range of temperature and chemical composition considered. By doing so the calculations are considerably simplified at the cost of the accuracy of the results. In order to make a reasoned decision, whether this simplification is desirable for particular systems and conditions, its impact on the accuracy of calculations needs to be assessed. The paper presents such evaluation by comparing results of modelling with a constant value of diffusion coefficient to results where the dependency of Di on temperature, chemical composition or both are added. The results show how a given deviation of diffusivity is correlated with the change in the final results. Simulations were performed in a single dimension for the FCC phase in Fe-C, Fe-Si and Fe-Mn systems. Different initial compositions and temperature profiles were used.

Rola termodynamiki w inżynierii materiałowej

Kędzierski Z.

Hutnik, Wiadomości Hutnicze

2004

Vol. 71, nr 7-8

292-297

Celem publikacji jest prezentacja potencjalnych mozliwości wykorzystania termodynamiki w inżynierii materiałowej. Na przykładzie dyfuzji wstępującej omówiono rolę potencjału chemicznego jako ogólnej siły pędnej dyfuzji. Zaprezentowae zostały podstawy teorii fluktuacji i niestabilności roztworów stałych. W części końcowej opisano problemy zwiazane z energia swobodną powierzchniową i termodynamiką powierzchni międzyfazowych.

The aim of the paper is outline generally usefulness of application basic thermodynamic concepts to materials science and engineering. The importance of chemical potential as general driving forceof diffusion is shortly discussed and examples of uphill diffusion are presented and explained. The role of composition flucuation in phase transformation and spinodal decomposition is also discussed. Finally fundamental problems of interface thermodynamics and effects of interface energy on phase diagram are presented.