Fabrication and synthesis of uniform TiO₂ nanoporous and nanotubular structures on dual-phase Ti–6Al–4V alloy using electron-beam irradiation

Developing homogeneous TiO₂ nanoporous arrays (NPAs) and nanotubular arrays (NTAs) on biphasic Ti alloys is challenging. The present study used large-pulse electron-beam (LPEB) irradiation prior to anodizing, and ascertained its effectiveness for developing homogeneous TiO₂ NPAs and NTAs on a dual (α + β)-phase Ti–6Al–4V alloy for the first time. The morphological features, structural characteristics, and corrosion resistance of the TiO₂ NTAs formed on the LPEB-irradiated Ti–6Al–4V alloy were compared to those obtained on the untreated alloy. The irradiation transformed the dual (α + β)-phase structure into a single α′-martensite phase with a uniform distribution of alloying elements, and enabled the formation of a smooth surface finish with reduced surface roughness. The modified surface facilitated the formation of homogenous NPAs and NTAs. Annealing in air at 500 °C for 2 h transformed the amorphous as-prepared TiO₂ NTAs into a mixture of anatase and rutile phases. Despite the appearance of cracks and an increase in intertubular spacing, the NTAs did not collapse. The NTAs formed on the untreated and LPEB-irradiated Ti–6Al–4V alloy provided better corrosion protection than their nonanodized counterparts.