Electron backscattered diffraction characterization technique for analysis of a Ti2AlNb intermetallic alloy

This investigation was conducted to ascertain the benefits of electropolishing after mechanical polishing for electron backscattered diffraction of a Ti2AlNb intermetallic Ti-21Al-29Nb (at.%) alloy containing the orthorhombic (O) and body-centered-cubic (BCC) phases. Electropolishing was performed at -40 degrees C in 6% H2SO4 methanol solution. Atomic force microscopy was used to measure the surface topography in attempt to correlate nano-scale surface roughness with electron backscatter diffraction pattern quality. The results suggest that mechanically polishing with colloidal silica (SiO2) or alumina followed by electropolishing is a sufficient surface preparatory technique for producing quality electron backscattered diffraction patterns for O + BCC microstructures. However, poor pattern quality results after mechanically polishing without electropolishing. High-quality orientation maps for O-dominated O + BCC microstructures were only possible through mechanical polishing followed by electropolishing. The data also suggest that surface roughness, on the order of 50 nm, has less effect on pattern quality than subsurface deformation. Overall, removing the near-surface damage was more critical than reduction of topography.