The structure and mechanical properties of thick cobalt electrodeposits

Cobalt electrodeposits have been produced in chloride solutions. Depending on the electrolysis parameters applied, two different structures for the electrodeposits, namely alpha and beta cobalt were observed. Their characterization included hydrogen content measurement, the relative volume fraction of the alpha and beta phases determined by X-ray diffraction, X-ray diffraction line profile analysis and microstructural investigation by optical microscopy, scanning electron microscopy and transmission electron microscopy. The influence of structure on mechanical properties was examined. The results showed that the ductility properties of the cobalt electrodeposits were highly sensitive to the structure. A higher beta phase content that was measured in some deposits did not improve the ductility due to the existence of trapped hydrogen which always exists in such deposits. However, annealing treatments seem to be a promising route to optimize the ductility of cobalt electrodeposits.