Low-dislocation-density ultrafine lamellar structure buffering triples ductility in Cu-8wt.%Sn alloy treated by rotary swaging and appropriate annealing

Breaking the strength-ductility trade-off in metal materials has always been a prominent topic in materials science. Here, we proposed a novel strategy of combining rotary swaging (RS) with appropriate annealing to construct an ultrafine lamellar structure with low dislocation density in Cu-8wt.% Sn alloy. This unique anisotropic structure achieves triple ductility without compromising strength compared with the traditional cold rolling process. Results show that the lamellar structure composed of alternating ultrafine-grained α-Cu and brittle Sn-rich phases can be significantly refined by RS, which can weaken stress concentration and thus reduce microcrack nucleation during tensile deformation. The lamellar ultrafine-grained α-Cu with low dislocation density has excellent strain hardening ability, which can effectively mediate deformation, and resist crack propagation and coalescence, thereby enhancing the ductility of materials. As a deformation method with industrial application capability, RS can construct a novel lamellar structure to overcome the strength-ductility dilemma, which deserves attention in materials science.