Interdiffusion in pseudobinary sections of Ni3Al–Co ternary system

Interdiffusion in Ni3Al intermetallic alloyed by 0–19 at.% Co was studied in three pseudo-binary sections: cAl=22, cCo=3.5, and cCo=16 (c in at.%). The experiments were carried out at temperatures between 1173 and 1473 K. An attempt was made to analyze the interdiffusion coefficient into intrinsic diffusivities of individual components. Since no detectable shift of tungsten inert markers was observed, it was concluded that the intrinsic diffusivities of element pairs with varying concentration (Al/Ni and Co/Ni) in respective pseudo-binary sections are approximately equal one to another. The interdiffusion in pseudo-binary alloys Al/Ni (cCo=const.) runs slightly faster than that in pseudo-binary alloys Ni/Co (cAl=const.). The relations between the measured interdiffusion coefficients in the Ni3−xAlCox ordered γ′ phase agree well with literature data for the interdiffusion coefficients in both the ordered γ′ and γ′+Co phases and also for the disordered Al–Ni and Co–Ni solid solutions. They are qualitatively explained by mutual interaction between constituents and by their interaction with vacancies.