An Al foil of 25 m thickness was used to produce a Ni/AI/Ni interconnection under isothermal conditions at 680(0)C. After dissolution of the Al filler metal in the Ni substrate, and Ni from the substrate in the All liquid foil, a solidification process occurred. First of all, the solidification was stopped just at the disappearance of the Al liquid metal, but also at different steps of the progress of solidification. Sub-layers of the two phases Al(3)Ni(2) and Al(3)Ni were revealed within the frozen joints. A solidification - segregation model was developed to describe the formation of the sub-layers of both mentioned phases. The model is able to predict solute segregation profiles across the sub-layers of the Ni/Al/Ni interconnection, taking into account a superposition of some phenomena like partitioning, back-diffusion into the solid and peritectic reactions. The value of the diffusion coefficient into the solid for the Al(3)Ni(2) phase formation in the presence of the liquid is also estimated.