Modification of the surface of copper and its alloys due to impact to nanosecond ultraviolet laser pulses

Abstract

In connection with the possible use of laser technological equipment in space the impact of nanosecond UV laser on copper and its alloys was investigated. At the pre-threshold mode, in the absence of obvious traces of melting, at an energy density of E = 0.1–1.0 J/cm 2 , the metal in the irradiated zone swelled up and traces of plastic deformation were found. The uplift arised as a result of the formation of an excessive number of point defects. With an increase of the number of impacting pulses, accumulation of damage occurred, despite the fact that the surface completely cools down during the time between pulses. The height of the resulting uplift reached 1 μm, and sometimes even slightly more. Sliding and cracking along grain boundaries occurred, as well as crystallographic slipping. The discovered effect of the impact of laser pulse on the metal surface, associated with the occurrence of uplift and the presence of plastic deformation, is similar to the well-known acoustoplastic, electroplastic, and magnetoplastic effects. The discovered effect was called optoplastic. Exceeding the laser damage threshold (E ∼ 1.0 J/cm 2 ) leads to melting and evaporation of the metal with the formation of a crater. This is oppositely directed process, which suppresses the manifestations of the optoplastic effect. • Copper surface modification due to nanosecond laser pulses impact was investigated. • An optoplastic effect was found. • It is of interest for the preparation of a metal surface for diffusion welding.