Nanosize Alloying in Metallic Films

摘要

The investigation of phase states and structural composition has been performed in wide ranges of temperatures and component concentrations in film systems of short-period Nb-Sn and Nb-Al layers produced by magnetron sputtering. The formation of primary niobium-based high-concentration solid solutions (HCSSs) observed with decreasing thickness of short-period layers of the alloy components is explained by the process of mixing upon the coalescence of small particles of different phases spontaneously melting because of thermofluctuation processes-a nanosize analog of alloying upon melting of components together (mixing by melting). Modified phase diagrams of Nb-Sn and Nb-Al systems have been constructed in concentration ranges of up to 25.5 at. percent Sn and 32.2 at. percent Al. Within these intervals, the solid solutions obtained by nanosize alloying are thermally stable up to the temperatures of the onset of the reactions of formation of corresponding intermetallic compounds ("intermetallization temperature"). In the niobium-aluminum system, prior to the transition of individual metal layers into a solid solution coherent superlattices of the initial phases are formed, with the lattice parameter a of the new unified lattice being close to a doubled lattice parameter of aluminum and the lattice parameter c being close to a doubled lattice parameter of niobium. An assumption is suggested that the qualitative shift of solubility toward higher values indicates a deeper character of mixing of components upon nanosize alloying than upon mixing by melting.