Effects of Hf content on nanotubular structure of Ti-29Nb-xHf ternary alloys

Abstract

In this study, the effects of Hf content on the nanotubular structure of Ti-29Nb-xHf ternary alloys were investigated. The Ti-29Nb-xHf ternary alloys had Hf concentrations between 0wt.% and 15wt.% and were manufactured using a vacuum arc-melting furnace. Formation of a nanotube structure on these alloys was achieved by an electrochemical method in a 1M H3PO4+0.8wt.% NaF electrolyte solution. The microstructures of the Ti-29Nb-xHf alloys changed from a needle-like structure to an equiaxed structure with increasing Hf content. The surface characteristics were analyzed by field-emission scanning electron microscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and a wettability test.The Ti-29Nb-xHf alloys had an equiaxed grain structure with α″+β phases, and the α″ phase disappeared with an increase in the Hf content. The Ti-29Nb-15Hf alloy showed higher intensity β-phase peaks in the XRD patterns compared to Ti-29Nb-3Hf and Ti-29Nb-7Hf alloys. The average length of the nanotubes increased and the nanotubes became highly ordered as the Hf content increased. The contact angles of the surface with the nanotubes were lower than those of surfaces without nanotubes.