Enhanced mechanical properties in Cu–Zn alloys with a gradient structure by surface mechanical attrition treatment at cryogenic temperature

This paper describes the effects of gradient structure on mechanical properties of Cu–Zn alloys processed by surface mechanical attrition treatment (SMAT) at liquid nitrogen temperature (77 K). This method leads to the formation of a gradient structure with surface fine-grained regions and a coarse-grained interior. In this study, a fine-grained surface layer with a thickness of 10 μm is formed on a coarse-grained Cu–Zn alloy sheet after the cryogenic SMAT process. Microstructural observations and microhardness measurements demonstrate that a significant microstructure refinement in grain size and a gradient increase in hardness from the coarse-grained core to the top surface. Tensile tests at room temperature showed superior strength–ductility synergy for the SMAT sample.