Effect of High-Power Ion Beams on the Surface Topography and Structure of the Subsurface Layer of Submicrocrystalline Titanium Alloys

Resumo

The influence of high-power beams of carbon ions (the ion energy is 250 keV; the pulse duration is ~100 ns; the current density in the pulse is 150–200 A/cm²; the surface energy density of a single pulse is j ~ 3 J/cm² under the irradiation of the samples of the VT1-0 titanium alloy and j ~ 1 J/cm² for the treatment of the samples of the VT6 titanium alloy; and the number of pulses is 1, 5, 10, and 50) on the surface topography and structure-phase state of the subsurface layer of submicrocrystalline titanium alloys VT1-0 and VT6 is studied. The sample surface before irradiation is preliminarily mechanically grinded and polished. It is shown that surface defects are formed on the alloy surface after irradiation. These are craters of various shapes and geometry with diameter from fractions of micrometer to 80–100 μm. Herewith, the grain structure in the subsurface layer becomes more uniform in size and degree of grain equiaxity. A rather homogeneous structure is characteristic of the state of the VT1-0 titanium alloy; the average grain size is ~0.31 μm, while that one the VT6 alloy is ~0.9 μm. The grain growth in the transverse direction to 0.54 μm is observed after one irradiation pulse in the subsurface layer of the VT1-0 alloy (at j ~ 3 J/cm²), while the grain size for the VT6 alloy (j ~ 1 J/cm²) decreases to ~0.54 μm. The average grain size in the subsurface layer after 50 pulses reaches ~2.2 μm for the VT1-0 alloy and ~1.6 μm for the VT6 alloy. It should be noted that a rather homogeneous grain structure with equiaxial grains is formed for both alloys already after the effect of one pulse of the high-power ion beam.