Diffusivity and atomic mobility for Fcc Ni-Ti-V alloys: Experiment and modeling

Ni-Ti-V is one key sub-system of the Ni-based superalloys. However, there is a lack of the investigation on diffusion kinetics for Fcc Ni-Ti-V alloys. In order to remedy this situation, we combined the diffusion couple experiment and calculation by CALTPP (CALculation of ThemoPhysical Properties) software to investigate diffusion kinetics for Fcc Ni-Ti-V alloys. Totally, 12 ternary Fcc Ni-Ti-V diffusion couples were prepared and annealed at 1273, 1373 and 1473 K, for which the composition profiles were measured by EPMA (Electron Probe MicroAnalysis). Based on the measured composition profiles and available thermodynamic descriptions, the interdiffusivities and atomic mobility parameters for Fcc Ni-Ti-V system were then calculated by the numerical inverse method integrated with CALTPP software. The simulated composition profiles by CALTPP software agree well with the measured ones. Moreover, the interdiffusivities obtained by CALTPP software were confirmed to be reliable through the good consistence with those calculated by M - K (Matano-Kirkaldy) method. Thus, the present numerical calculation by CALTPP software was verified to be reasonable. Finally, based on the presently obtained mobility parameters and available thermodynamic descriptions for Fcc Ni-Ti-V alloys, the threedimensional surfaces of the interdiffusivities, activation energies and frequency-factors against Ti and V composition were predicted. The present work provides reliable kinetic parameters for Fcc Ni-Ti-V alloys, which can be included in the diffusion database of Ni-based superalloys for material design.