Microstructure of polycrystalline Ti and its microelectrochemical properties by means of electron-backscattering diffraction (EBSD)

The electrochemical behaviour of polycrystalline materials is determined usually by grain orientations. The correlation between crystallographic orientation and electrochemical behaviour is examined on titanium as example by combining microelectrochemical techniques with orientation measurements carried out with electron-backscattering diffraction (EBSD). The results will be compared with former experiments in which crystallographic data were analysed with anisotropy rnicroellipsometry (AME). Whereas AME is only capable to deter-mine a single Euler angle phi, EBSD analysis reveals all three Euler angles. For a clear crystallographic determination of the metal surface on hexagonal titanium, it is sufficient to determine the Euler angles phi and phi (2). The angle phi (1) can be neglected. For phi < 45 degrees, the angle phi (2) has an almost negligible influence on the electrochemical behaviour. The oxide layer thickness can be characterised by the analysis of the EBSD pattern quality. Due to the fact that oxide films on different titanium grains show different interference colours, it is possible to correlate interference colours of oxide films formed at U= 15 V with the crystallographic orientation of the underlying grains which have been determined by EBSD orientation mapping. With the help of this orientation/colour correlation, the grain orientations can be estimated quickly with a microscope. (C) 2001 Elsevier Science Ltd. All rights reserved.