Diffusion and Atomic Mobility for FCC Ni-Si-Ti Alloys: Experiment and Modeling

Abstract

The Ni-Si-Ti system plays an important role in high temperature structural materials. Accurate atomic mobilities of fcc Ni-Si-Ti system are essential for the microstructure simulation of Ni-based superalloys. In the present work, diffusion couples of fcc Ni-Si-Ti system have been prepared and annealed at 1273, 1373 and 1473 K. By combining solid/solid diffusion couples with the electron probe microanalysis (EPMA) technique, the interdiffusivities in fcc Ni-Si-Ti were calculated via Matano-Kirkaldy method and numerical inverse method. Based on the reliable thermodynamic description and interdiffusion coefficients measured above, two sets of atomic mobilities were optimized by means of the CALTPP (CALculation of ThermoPhysical Properties) program. These atomic mobilities can reasonably describe the diffusion behaviors by comparing model-predicted diffusivities, concentration profiles and diffusion paths with the experimental ones. Besides, based on these atomic mobilities, three-dimensional surfaces for the interdiffusivity at 1273, 1373 and 1473 K were plotted. Furthermore, three-dimensional planes of the activation energy and frequency factor were evaluated using the Arrhenius equation.