Tailoring elastic, mechanical and texture properties of Cu-37Zn brass by ultrasonic impact treatment applied at ambient and cryogenic temperatures

Abstract

The study examines the changes in elastic parameters and mechanical properties and the evolution of texture of thin plate specimens of Cu-37Zn alloy strain-induced at room and cryogenic temperatures using ultrasonic impact treatment (UIT) with wave-reflecting anvil. The precise measurements of the mass densities (ρ) and bulk-wave ultrasonic velocities (vij) by means of the pulse-echo method using a home-made automated apparatus provides quantitative data regarding the Debye temperature TD, elastic (E), shear (G) and bulk (B) moduli, Poisson coefficient (η), hardness HV, and Milman’s plasticity parameter δH, of the UIT-processed specimens. In addition, XRD, EBSD, TEM, and SAED analyses are used to characterize crystallographic texture and microstructure evolutions. As shown, the surface severe plastic deformation induced by multiple impacts during the UIT processing accompanied by ultrasonic vibrations results in an increase in TD, E, G, and HV and a decrease in η, B, and δH, which are more pronounced for air-UIT. Unusual dislocation activity is promoted by ultrasonic vibrations. Observed twinning and shear bands in cryo-UIT-ed specimen provide to the formation of the brass-type texture while the stress relaxation, unusual dislocation activity stimulated by ultrasonic vibrations and dislocation cell formation in the air-UIT-ed specimen leads to the copper-type texture. The longer UIT provides the nanostructuring regardless of the involved microscopic mechanisms and used temperature conditions.