Grain- and interphase boundary diffusion in eutectic AlCoCrFeNi2.1 compositionally complex alloy

Zhang H.; Mohan Muralikrishna G.; Akbari A.; Rösner H.; Tyler B.J.; Divinski S.V.; Wilde G.

Abstract

Short-circuit diffusion of Ni in the multi-principal element eutectic AlCoCrFeNi2.1 alloy is investigated, differentiating the contributions of grain- and interphase boundaries. The analysis is supported by grain boundary diffusion measurements in the constituting single-phase FCC and B2-ordered AlCoCrFeNi non-equiatomic alloys. The tracer diffusion measurements are performed in Harrison's B- and C-type kinetic regimes applying the 63Ni radioisotope. Analysis of the Ni grain boundary diffusion rates in the three alloys substantiates enhanced interphase boundary diffusion in the eutectic alloy outperforming the contributions of GB diffusion in the single-phase fractions. The distinct branches of interface diffusion in the eutectic alloy are related to the presence of FCC/B2 interphase boundaries with ideal and strongly non-ideal orientation relationships between the constituting phases. The correlations of the chemical complexity and the distortions of the crystal lattice with the GB diffusivities in high-entropy alloys are discussed.