Evolution of the preferred crystallographic orientation across the thickness of nickel electrodeposits

Numerous industrial applications of nickel electrodeposits, like for example as microcomponents, essentially depend on their preferred crystallographic orientation. As a function of the electrodeposition conditions, the microstructure can be tailored with respect to the size, shape and crystallographic orientation of grains. Thorough microstructure characterization, however, is not straightforward, because the microstructure of electrodeposits often changes across the thickness of the deposits and numerous twin orientations even with nano-size dimensions can evolve during growth of the deposits. This requires depth-dependent microstructure analysis with adequate resolution. Among the various available microscopic and diffraction based microstructure characterization techniques, electron backscatter diffraction analysis (EBSD) along the cross section of electrodeposits is particularly favored for such advanced investigations. The present work reports on the evolution of the preferred crystallographic orientation on the example of various fiber textured nickel electrodeposits. Tailored electrodeposition provided nickel deposits with different fibre textures being <211>, <100>, <110> and <210>. Quantitative texture analysis carried out by means of X-ray diffraction from the surface revealed the overall texture as an absorption-weighted average over the deposit thickness, but cannot reveal the required depth resolution. Therefore, it is supplemented by EBSD on cross sections of the electrodeposits. This provided the evolution of preferred grain orientations (including twins) as a function of distance from the substrate. The results revealed that electrodeposits on amorphous substrates develop a rather strong texture at the early stage of growth which is different from the texture dictated by the electrodeposition conditions.