Effect of different SMAT treatment times on pure copper in liquid nitrogen environment

Surface mechanical attrition treatment (SMAT) was conducted on annealed copper sheets under liquid nitrogen for 30 s, 60 s and 120 s. The yield strength of SMAT samples was improved by 2−5 times compared to annealed pure copper by quasi-static tensile, in which the yield strength of SMAT 60 s samples was increased by 211.3% compared to annealed pure copper, while the uniform elongation could still be maintained at 24.6%. Combined with the hardness test and metallographic observation, it was found that an obvious gradient structure was formed from the surface to the core of the treated sample. All results show that the samples after 60 s SMAT treatment have an optimal strength-ductility combination.