Assessment of the Diffusion Mobilities in the Gamma Prime and B2 Phases in the Ni-Al-Cr System
Carelyn E. Campbell
This work presents the assessment of the diffusion mobilities in both the Gamma prime and B2 phases in the Ni-Al-Cr system utilizing the phenomenological model developed by Helander and Agren. Available experimental tracer diffusivity, interdiffusion coefficients and activation energies were evaluated and then used to optimize the composition and temperature dependent diffusion mobilities. For both the B2 and the Gamma prime phases, the assessed diffusion mobility descriptions reproduce the Arrhenius temperature dependence for the Ni, Al, Cr tracer diffusivities and interdiffusion coefficients. The assessment reproduces the strong composition dependence of the diffusivities in the B2 phase observed experimentally. The measured composition dependences of the diffusivities in the Gamma prime phase are also replicated by the present mobility descriptions. The assessed mobility descriptions are tested by comparing calculated and measured composition profiles for a variety of Ni-Al and Ni-Al-Cr diffusion couples, including B2/B2, Gamma/Gamma prime, and Gamma/B2 couples.