Highly Ordered Nanotube Formation on Beta Typed Ti–xTa Alloy Surface

In this study, the highly ordered nanotube formation on beta typed Ti–xTa alloy surface was investigated. The Ti–xTa binary alloys were manufactured using a vacuum arc-melting furnace with varying Ta contents (10, 30, and 50 wt%), and then homogenized by heat treatment at 1050 °C for 1 h. The nanotube formation of Ti–xTa (x = 10–50 wt%) alloys were performed using a DC power source of 30 V in 1.0 M H₃PO₄ + 0.8 wt% NaF electrolyte solution for 2 hrs. The surface characterization was performed using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The microstructure of Ti–xTa alloy showed martensite structure α′, α″-phase, and a ′-phase structure. As the Ta content increased, the needle-like structures of α′ and α′-phase gradually disappeared and only the equiaxed structure of β-phase appeared. Nanotube morphology of Ti–xTa alloy changed according to Ta content. As the Ta content increased, the size of the nanotubes decreased and the number of the smaller nanotubes increased. In the cross-sectioned nanotube layer, the gap size between the nanotubes decreased as the Ta content increased.