Experimental investigation of diffusion behaviors in γ and γ’ Ni–Al–Co alloys

Abstract

On the basis of 13 groups of single-phase diffusion couples together with electron probe microanalysis technique, the composition profiles in γ and γ′ Ni–Al–Co systems at 1373–1523 K were measured. Atomic mobilities in γ Ni–Al–Co alloys were directly assessed from 9 groups of concentration profiles by means of HitDIC software. The established atomic mobilities contain only two interaction parameters, and their reliability was verified by comprehensively comparing the model-predicted concentration profiles with the experimental data in the literature and the present work. After that, the composition-dependent interdiffusion coefficients along the entire diffusion path in γ and γ′ Ni–Al–Co alloys were also evaluated at 1373–1523 K by using HitDIC. D˜AlAlNi and D˜CoCoNi in γ Ni-Al-Co alloys were validated by the results obtained by Matano-Kirkaldy method and the corresponding experimental values in Ni-Al and Ni-Co binary alloys. Comprehensive comparisons between the interdiffusion coefficients in the present work and those reported the literature validated the reliability of the presently evaluated interdiffusivities in γ’ Ni-Al-Cr alloys. The influences of Al and X contents on the D˜XXNi in γ Ni-Al-2 at% X (X= Co, Rh, Ta, W, Re, Os, and Ir) alloys and D˜AlAlNi in γ Ni-2 at% Al-X alloys were further discussed.