Solid-state interaction between nanofilms of aluminium and nickel in multilayer formed by sequential deposition is considered. Phase-formation sequence during reaction is discussed. The first phase, which appears in reactional diffusion, is determined by means of the methods of phenomenological simulation and molecular dynamics. As shown, in case of direct contact of pure nickel and pure aluminium at the temperatures above 700 K, the first intermediate phase should be liquid solution. Such contact melting follows from the metastable phase diagram calculated under assumption of suppression of the intermetallic-phase nucleation. The direct MD simulation confirms the decrease of the melting temperature of aluminium due to the dissolution of nickel in it. The computer model of deposition of the nickel atoms onto the aluminium nanofoil is presented. The influence of temperature and density of flux on the deposition process and on structure formation in the contact region is demonstrated. If the deposition proceeds under quite high temperature, the ordered phase based on b.c.c. lattice appears in the process of deposition. Its presence makes contact melting impossible. If deposition proceeds at room temperature, some partial ordering in the form of ordered 2D-islands in the contact zone is possible, but it does not prevent the contact melting. Possible influence of oxides is neglected within this model.