Surface morphology of titanium irradiated by high-intensity pulsed ion beam

Surface morphology of pure Ti irradiated by high-intensity pulsed ion beam (HIPIB) with ion current density of 60-250 A/cm(2) and shot number of 1-30 at 220 kV has been investigated by using profilometer, scanning electron microscopy and atomic force microscopy to explore the interaction mechanism between HIPIB and metallic materials. Two kinds of samples were prepared with different initial surface roughness (R-a), i.e. high-roughness and low-roughness Ti, respectively. A similar change trend of R-a was found on the irradiated surfaces for both the two kinds of samples that increase of the R-a was obtained with few shot number and then continuous decrease of the R-a to a surface smoothing was with multi-shot irradiation. However, the increase of R-a on the irradiated low-roughness Ti was greatly limited as compared to the high-roughness case. It is demonstrated that surface smoothing and roughening of irradiated Ti can be realized under optimization of the parameters by combining adjustments of ion Current density and shot number. The morphology features on the irradiated high-roughness Ti were craters and waviness for roughened surfaces and some vague or apparent texture with disappearance of the craters for smoothed surfaces. For the low-roughness Ti, no distinct craters were formed except for some obvious texture. The micro-non-uniformity (micro-protrusions) on the irradiated surfaces causes the cratering on pure Ti by inducing a selective ablation under HIPIB irradiation. The locally more intense liquid evaporation and droplet ejection from the irradiated surfaces of different morphologies led to disturbance of the molten surface layer in the different scales, resulting in the surface roughening and smoothing. (C) 2003 Elsevier B.V. All rights reserved.