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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.

Modelowanie mikrostruktury i własności stali DP po walcowaniu na gorąco i chłodzeniu laminarnym

Pernach M., Pietrzyk M.

Hutnik, Wiadomości Hutnicze

2011

Vol. 78, nr 8

657--662

Praca przedstawia model numeryczny przemian fazowych w stali DP zachodzących podczas walcowania na gorąco i chłodzenia laminarnego. Model oparty na rozwiązaniu MES równania dyfuzji z ruchomą powierzchnią międzyfazową pozwolił na wyznaczenie ułamka objętości faz, wielkości ziarna i rozkładu koncentracji węgla w austenicie w zmiennych warunkach temperaturowych. Wyniki symulacji numerycznych posłużyły do opracowania zależności pomiędzy mikrostrukturą i własnościami mechanicznymi stali DP.

Numerical model of phase transformation occurring during hot rolling and laminar cooling in DP steel is presented in this paper. The model, which is based on FEM solution of a diffusion equation with a moving boundary, allows to determine ferrite and martensite volume fraction, grain size, carbon segregation before the front of transformation in fluctuating temperature conditions. Results of numerical simulations were used for development of the relationship between microstructure and mechanical properties of DP steel.