Interdiffusion and diffusion paths in two-phase gamma plus beta vertical bar gamma plus beta diffusion couples. Comparison of experimental investigation with theoretical predictions

摘要

The first-ever experimental results concerning the interdiffusion in the two-phase, gamma+beta region of the ternary system are presented, together with the theoretical interpretation of the observed phenomena. In the experimental part of the study, a number of two-phase diffusion couples made from cast Ni-Cr-Al alloys was studied at 1200 degrees C. The application of the novel wide-line Energy-dispersive X-ray Spectroscopy (WL-EDS) allowed for previously impossible quantitative measurements of the concentration profiles within the two-phase zones. The measured profiles, together with the determined diffusion paths, were compared to the results of the simulations performed with the use of two different models: the Engstrom et al. model (DICTRA) and multi-component multi-phase model. The results allowed verifying the existence of a number of previously postulated features typical for the multi-phase diffusion. The comparison of the experimental and simulated results confirms that the currently used theoretical models of the interdiffusion process enable a satisfactory description of the real process. Still, some of the observed features cannot be interpreted in the light of available theory, although some of them are likely caused by the non-uniform cast microstructures. The better agreement with the experimental data obtained with the use of multi-multi model suggests that the interdiffusion should be considered simultaneously in all phases present in the system. (C) 2020 The Authors. Published by Elsevier B.V.