Formation of a Diffusion Zone at the Interface of Nickel/Aluminum Bimetal

Abstract

In this paper, a study of a diffusion zone at the nickel/aluminum interface is carried out. Bimetallic samples constructed from pressed plates of Nickel and Aluminum have been annealed in a vacuum furnace at a temperature above the melting temperature of aluminum. Formation patterns of diffusion zones are investigated using the samples with different intervals of annealing time. Sintered samples have been cut across the boundaries of the section; the cut surface has been polished.Analysis of experimental results shows that the increase of diffusion process thermal activation time leads to the increase diffusion zone width. For this zone, the measured microhardness is a function with its maximum that indicates the nature of the phase components distribution at the Nickel/Aluminum interface. According to the Ni-Al phase diagram, the widest homogeneity range and, consequently, greater probability of formation of intermetallic compounds, have NiAl and Ni3Al phases. The diffusion zone itself is a macroscopic object at the interface of Nickel/Aluminum bimetal, thereby, showing the macroscopic diffusion of diffusants.Measured diffusion parameters of the diffusion zone at the interface of bimetallic sample demonstrate the increase of diffusion coefficient with the increase of exposure time at 700 0C. Apparently, this behavior is due to the formation of branched intergranular and interphase boundaries during the synthesis of intermetallic compounds in the diffusion zone. The combination of intermetallic phases and solid solutions determines the strength properties of the diffusion zone, and, consequently, the adhesion strength of the bimetallic compound.DOI 10.14258/izvasu(2018)1-04