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 ß-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.

Functional Elements Coatings on the Plasma Electrolytic Oxidation-Treated Ti-6Al-4V Alloy by Electrochemical Precipitation Method.

In this study, functional elements coatings on the plasma electrolytic oxidation (PEO)-treated Ti-6Al-4V alloy by electrochemical precipitation method were investigated. Ti-6Al-4V ELI disks were used as specimens for PEO and HA coating. The applied voltage and time were selected to be 280 V and 3 minutes for PEO treatment, respectively. The electrochemical precipitation on the Ti-6Al-4V alloy was carried out using cyclic voltammetry with cycle of 3, 5, 10, and 20 from -1.5 V to 0 V (vs. SCE electrode) in electrolyte containing Ca, P, Mg, Mn, Sr, Zn, and Si ions by cyclic voltammetry after PEO treatment. The morphology changes of the coatings on the PEO treated Ti-6Al-4V alloy surface were observed using FE-SEM and EDS. PEO surface has a uniformly distributed circular shape and a porous surface and the deposition of low cycles in electrolyte containing Mg, Mn, Sr, Zn, and Si-HA coated surfaces show uniform circular and granular structures. The precipitates of Mg, Mn, Sr, Zn, and Si-HA on the PEO treated surface showed a large number of circular particles as the number of deposition cycles increases with a mixture of rod-shaped particles and petal-shaped particles around pores. The precipitate nucleates around the pore and grows rapidly as the cycles increase.