Microstructure and Deformation Behavior of High Strength Pure Cu Bulk Material Manufactured by Cold Spray Process

This study investigated the effects of strain, strain rate, tension-compression asymmetry, and carrier species (He, N₂) on the microstructure evolution and deformation behavior of high strength copper materials manufactured by cold spray process. Initial microstructural observation identified bimodal microstructure with grain size of hundreds of nm in the particle interface area and relatively coarse grains in all other areas. Room temperature compressive results confirmed cold sprayed Cu to have the yield strengths of 340 ~ 415 MPa with strain rate. In addition, strain softening phenomenon, which is rarely found in room temperature deformation, was occurred. Cold sprayed Cu bulk material showed low strain rate sensitivity. To analyze the deformation behavior of the cold sprayed Cu material, constitutive model considering work hardening and softening was employed. Tensile test results of cold sprayed Cu material represent similar yield strength value and almost no plastic deformation behavior compared to those results obtained by compression test. Compressive yield strength of cold sprayed Cu material using He carrier gas was significantly higher than that of using N₂ carrier gas. The deformation and fracture mechanisms of cold sprayed Cu bulk material were also identified based on the results of EBSD analysis and FE-SEM fractograpy results.