Modifying the structural phase state of fine-grained titanium under conditions of ion irradiation

The results from quantitative investigations into the structural phase state of finely dispersed titanium before and after implantation with aluminum ions are presented. Two types of α-Ti grains differing by phase composition, defect structure, and size are distinguished in the structure: fine grains in the range of 0.1-0.5 μm and coarse grains in the range of 0.5-5 μm. The presence of two types of TiO₂ particles in the material, i.e., rounded particles found at dislocations in the bulk of the α-Ti grains and lamellar particles found only inside coarse α-Ti grains, is established. The formation of the Ti₃Al phase is observed in the form of lamellar inclusions along the grain boundaries and rounded particles in triple joints. It is found that the particles of the TiAl₃ phase are isolated with a smaller volume fraction than the Ti₃Al phase; they are localized along the boundaries of coarse grains of the titanium matrix. It is established that the granular state and defect structure of the material change substantially after ion irradiation; i.e., the dislocation density and the fields of internal stresses in fine grains grow considerably, relative to the initial state of titanium.