Formation of the surface relief in niobium in the process of electrotransport

The study concerned the formation of a surface microrelief on heating of niobium by electric current. The electrotransport was conducted in a vacuum chamber at a residual pressure of 5x10-7 Pa for 30-100 h. The surface was investigated with the aid of a light microscope, an interferometric attachment and a microanalyzer. Three types of surface defects: pits (bosses), grain boundary grooves and microrelief formed with strips or waves were detected in high-temperature electrotransport in vacuum of 5x10-7 Pa