Physical base of the metallic gradient surface layers of titanium alloys formed under ion implantation

The results of microstructure and phase composition investigations of titanium in different structural states (with average grain sizes of 0.3 μm, 1.5 μm, 17 μm, 38 μm) implanted by Al ions using the «Raduga-5» and MEVVA-V.RU sources are presented. The size, shape and localization of the formed phases (TiO₂, Ti₂O, TiC, Ti₃Al, TiAl, Al₃Ti) depend strongly on the grain size of titanium target. In polycrystalline titanium after implantation by Al-ions the secondary phases (Ti₃Al, TiAl, TiO₂, TiC) formed in the body of grains of titanium matrix. It is shown that the nanostructural particles of TiO₂ phase are located mainly on dislocations in the body of target grains. An ordered Ti₃Al phase is located at a depth of more than 200 nm in the implanted layer along the boundaries of the titanium grains. The TiAl₃ phase formed on the grain boards in subnano- and microstructural state of titanium targets. The improvement of the mechanical properties of titanium due to formation of the gradient structure of ion-alloyed surface layer was obtained.