Effect of ion beam treatment (Ar+, E=30 keV) on the microstructure of titanium alloys

The effect of continuous Ar+ ion beams (E = 30 keV, j = 400 mu A/cm(2); F = 5.10(16) cm(-2)) on the hardness and microstructure of the Gr2-titanium-based and Ti-6Al-4V alloys after cold working and subsequent recrystallization annealing is studied. It has been found that the initial microstructure of the annealed alloys in the equilibrium state, which consisted of recrystallized equiaxed grains, does not change after irradiation; thus the hardness of the irradiated samples is comparable with that of the initial samples. The initial fine fiber structure of the deformed Ti-6Al-4V alloy changes insignificantly after both annealing (T = 790 degrees C, 30 min) and ion irradiation under used conditions. In contrast to that, the effect of rapid radiation annealing of the cold-worked titanium Gr2 alloy with beams of accelerated ions of inert gas at low temperatures (lower by 130 degrees C than the conventional annealing temperature of these alloys at 680 degrees C) and for a shorter time (9 min instead of 35 min, t(irr) similar to 20 s) has been revealed. The result is the formation of a uniform recrystallized structure with equiaxed fine grains 5-10 mu m in size in the entire volume of the 3-mm-thick samples, despite the fact that the average projected range of 30-keV Ar+ ions in titanium is only 20 nm.