Papers by Author: Renata Bachorczyk Nagy

Abstract: We compare the experimental and computed results of the stress assisted interdiffusion. The Cu-Fe-Ni diffusion couples were investigated at 1273 K. The alloys in this system do not form ideal solid solutions and consequently the Calphad method was used to compute the elements activities. The method applied in this work base on the Darken’s drift velocity concept, Vegard law and Navier-Lamé equation. It allows computing the deformation field during the interdiffusion process. The driving force for diffusion in such a ternary system is the gradient of the chemical potential which can be calculated from the concentration profiles and using the known thermodynamical data of the system. Comparison between the Darken method without stress and the influence of stress on the interdiffusion in the Cu-Fe-Ni system is presented. Simulations that take into account the deformation field give better fit to the experimental results. Moreover we show qualitative and quantitative differences between the simulations of interdiffusion using the Calphad method and with the ideality sweeping statement.

Abstract: The oxidation resistance behaviour of a number of surface-treated FeCrAl commercial alloys and some model alloys of well-defined composition, incorporating a range of reactive elements in trace amounts, has been studied under thermal cyclic conditions in air with and without additions of water vapour. Additions of reactive elements such as Zr, La, Y, Hf modify the oxidation resistance behaviour of FeCrAl-alloys by improving the scale adherence and consequently may extend the lifetime of FeCrAl steels. The presence of the water vapour can affect oxidation in a number of different ways. Our results may indicate that high content of water vapour can cause the lives of such alloys to be decreased. This work forms part of a larger European-funded project to evaluate physical properties, microstructural features, oxidation/corrosion resistance and lifetime improvement. The correlation between alloy parameters and lifetime; as well as the modeling of oxide scale behaviour as function of cycling conditions is also studied.

Abstract: Interdiffusion in Co-Fe-Ni alloys was studied in 1373-1588 K temperature range. The Danielewski-Holly model was used for the description of the interdiffusion process in ternary Co- Fe-Ni diffusion couples both for the finite and infinite geometry. Using the inverse method the average intrinsic diffusivities of components in the Co-Fe-Ni system were calculated and compared with the results of the other authors. The activation energies of cobalt, iron and nickel intrinsic diffusion have been found in 1373-1588 K temperature range.