Corrosion Behaviour of Electron Beam Melted Ti6Al4V: Effects of Microstructural Variation

Abstract

Microstructural analysis and electrochemical measurements were carried out on longitudinal and transverse planes of an additively manufactured (AM) Ti–6Al–4V rod printed in the horizontal direction by electron beam melting (EBM), and compared with those performed on a commercially available alloy. Microstructural differences in the planes parallel and perpendicular to the build direction were characterized using optical and scanning electron microscopy, X-ray diffraction, and transmission electron microscopy coupled with energy dispersive spectroscopy. The microstructures of three different locations along the transverse axis on the EBM samples were also studied. The starting point, the middle, and the end of the sample in the build direction consisted primarily of α-phase and a small amount of β-phase. On progressing from the starting point towards the end of the build, the size of both phases increased and the elemental distribution of alloying elements showed more segregation of vanadium and iron into the β-phase. The electrochemical behaviour was studied as a function of time using electrochemical impedance spectroscopy and potentiodynamic polarization. The film resistance of the wrought sample was slightly better than those of the EBM samples. The film resistance of the EBM-transverse sample improved slightly more with exposure time than that of the longitudinal sample.