Diffusivities and atomic mobilities in the Ni-rich fcc Ni-Al-Cu alloys: experiment and modeling

The diffusivities along the whole diffusion path in one diffusion couple of Ni-rich fcc Ni-Al-Cu alloys at 1273, 1333 and 1433 K are obtained by means of the numerical inverse method. In total 12 diffusion couples are used to obtain the diffusivities at the intersections in the diffusion paths by the Matano-Kirkaldy method. Two sets of atomic mobilities are assessed using the CALTPP program based on the diffusivities calculated by the numerical inverse method and Matano-Kirkaldy method, respectively. The validity of the obtained atomic mobilities is confirmed by comparing the model-predicted diffusivities, concentration profiles and diffusion paths with the measured ones. The whole calculation by the numerical inverse method in CALTPP with higher efficiency can achieve the same accuracy as the Matano-Kirkaldy method. The present study demonstrates that one diffusion couple combined with the numerical inverse method can reliably assess the atomic mobilities for fcc Ni-Al-Cu alloys.