In Vitro Corrosion Anisotropy Assessment of Ti6Al4V Bimodal Microstructure due to Crystallographic Texture

The effect of crystallographic texture on the corrosion performance of the Ti6Al4V alloy with a typical bimodal microstructure has been studied on three orthogonal surfaces of the rectangular sample. The optical microscopy (OM) and scanning electron microscopy (SEM) observations revealed that the same microstructure is developed on three surfaces via heat treatment. The crystallographic planes, which are located in parallel to each surface, have been evaluated through macrotexture analysis. The electrochemical measurements showed that the RD-ND surface (i.e., surface normal to transverse direction), in which \( \left\{ { 0 0 0 2} \right\} \) and \( \{ 11\bar{2}0\} \) crystallographic planes are placed in parallel to the surface, has the lowest corrosion rate equal to 2.2 × 10⁻⁵ mm/year. In contrast, the corrosion rate of the TD-ND surface, which is normal to the rolling direction, with \( \left\{ { 1 0\bar{1} 0} \right\} \) planes in parallel to the surface is ~ 15 times greater than that of the RD-TD surface. Electrochemical impedance spectroscopy (EIS) results showed that the greater corrosion resistance of different surfaces is mainly dependent on the passive layer properties formed on each surface.