The effect of large-area pulsed electron beam melting on the corrosion and microstructure of a Ti6Al4V alloy

Graphical abstract: - Highlights: • Ti–6Al–4V alloy was large area electron beam melted at 1.38 J/cm² energy density. • An alpha prime martensitic phase transformation occurred at the surface. • The surface martensite enhanced the corrosion rate by two orders of magnitude. • The treatment reduced the surface roughness and improved surface wettability. - Abstract: The use of titanium alloys in biomedical applications continues to increase due to the excellent stiffness to weight ratio and high corrosion resistance. In order to improve the surface wettability and corrosion properties of a Ti–6Al–4V alloy, the surface treatment method, large area electron beam melting technique was investigated. Polished samples were subject to pulsed treatments of 1, 15 and 25 at 1.38 J/cm² beam energy. Surface roughness and contact wetting angles were reduced as a result of the treatment. Microstructural analysis of the surface by XRD and FIB-TEM revealed a martensitic alpha prime phase formed as a result of the high cooling rates induced by the treatment. The presence of this homogenous martensite layer was shown to facilitate a compact passive oxide layer formation during corrosion, thus improving corrosion rates by several orders of magnitude compared to an untreated sample. Large area electron beam melting of Ti–6Al–4V induced a number of changes to the near surface microstructure of the samples, all of which could be used to tailor mechanical and corrosion properties to that of a desired application, without compromising the bulk material properties. These are explored in detail in this work