Diffusion behavior of fcc and L12 Ni–Al–Cr alloys

Abstract

In this paper, 12 groups of single-phase (γ and γ′) Ni–Al–Cr diffusion couples were carefully fabricated, and their concentration profiles at 1423, 1473, and 1523 K were measured by means of electron probe microanalysis technique. Atomic mobilities of γ phase in ternary Ni–Al–Cr system were then established directly from the experimental concentration profiles by using the HitDIC (High-throughput Determination of Interdiffusion Coefficients) software. The reliability of the atomic mobilities was confirmed by the coincidence between the calculated and experimental properties including the composition profiles and diffusion paths. Moreover, based on the atomic mobilities together with the available thermodynamic descriptions, the three-dimensional interdiffusivities planes at 1423–1523 K were constructed, from which the activation energies in γ Ni–Al–Cr alloys were extracted. Lower diffusion activation energy corresponds to higher interdiffusion coefficient. After that, the composition-dependent interdiffusion coefficients in γ′ Ni–Al–Cr alloys were determined and the magnitude relation of D˜AlAlNi and D˜CrCrNi in γ’ Ni–Al–Cr alloys was verified.