Study on the surface modification of nanostructured Ti alloys and coarse-grained Ti alloys

Abstract

Commercial purity titanium (CP-Ti) and a Ti-6Al-4V alloy (Ti64) were processed by high-pressure torsion (HPT) to 10 and 20 turns. The HPT processing produced a nanostructured microstructure and a significant strength enhancement in the CP-Ti and Ti64 samples. After 20 turns the samples of HPT-processed CP-Ti and Ti64 were subjected to laser surface treatments in an air atmosphere using different scanning speeds and laser powers. The surface roughness of the laser-modified samples increased with increasing laser power and this produced a hydrophilicity due to a lower contact angle. After a holding time of 27 days, these samples underwent a hydro-philic-to-hydrophobic transformation as the contact angle increased from 13 to as much as 120 for the CP-Ti sample and for the Ti64 sample the contact angle increased from 10 to 126. In addition, the laser surface modification process was carried out with different atmospheres (air, vacuum and O2) on heat-treated but unstrained CP-Ti and Ti64 samples and the contact angle changed due to the surface element content. Thus, as the carbon content increased from 28% to 47% in CP-Ti in vacuum environment, the surface contact angle increased from 22 to 140. When a laser surface modifi-cation process is conducted under oxygen-less conditions, it is concluded that the contact angle increases rapidly in order to control the hydrophobic properties of Ti and the Ti alloy.

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Identifiers

ORCID for Yi Huang: orcid.org/0000-0001-9259-8123

ORCID for Terence G. Langdon: orcid.org/0000-0003-3541-9250

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