Phase and structural transformations in copper and its alloys under the electrolytic discharge

Abstract

Copper and its alloy were treated in an electrolytic plasma formed in the boron-containing electrolyte under the action of discharge in order to obtain a diffusion coating with enhanced hardening characteristics and the structural changes in the surface layer of the metal that occur in this case were studied. As a result of processing in electrolytic plasma, characterized by high heating and cooling rates, a diffusion layer was formed on the surface of copper and an alloy based on it (brass). The layer contains nanosized inclusions of copper borides, ternary compounds Cu-B-H, Cu-B-O concentrated mainly along grain and phase boundaries and providing hardening of the metal surface. The action of the discharge provides structural and phase transformations in the metal, the deformation of the grains - elongation in the direction of the driving force (electric transfer) at a depth of 100 μm and the creation of metastable states in the surface layers. Moving vacancies and compressing atoms in the direction of the force create conditions for the rapid movement of boron atoms. With increase in current density and time of treating, the size of nanostructures decreases. Their size is of the order of 6-16 nm. Obtaining wear-resistant coatings on copper and its alloys, which include phases containing copper and boron, increases the strength characteristics of copper and its alloys by 1.5-2 times.