Micro-nano interface structure and mechanical characteristics of thin wall Cu/Al composite tubes prepared by strong staggered spinning

In this paper, a method of stamping first and then strong staggered spinning was studied to process Cu/Al laminated composite into thin-walled composite tube. The multi-scale interfacial structure, element diffusion, microscopic evolution, mechanical properties and fracture mechanism of the tubes with different thickness reduction (TR) were studied by different material characterization methods. The results show that with the increase of TR, the interface experienced brittle layer fracture, fresh metal extrusion, new diffusion layer and the formation of the interface, and always maintained a good combination. Under the shearing force of the outer rotating wheel, the grain sizes of both sides of Cu and Al with 80%TR are reduced to 0.75 mu m and 1.15 mu m by 82% and 80% refinement, respectively. The deformation of Cu is induced by work hardening and dynamic recrystallization (DRX), and the strain inhomogeneity caused by (111) fiber is transferred from grain boundary to interior with the increase of TR. The Al side is mainly dominated by dynamic recovery (DRV), and the grain presents random and uneven strain, and finally changes to the internal grain strain mutation dominated by (001) fiber. The Cu grains near the rotating wheel are elongated at an inclination of 45 degrees, but others at the interface are fine and equiaxed, suggesting good deformation coordination at the interface. The deformation coordination and strain transfer are stimulated by the change of micro-nano mechanical properties of Cu, interface and Al. Compared with the initial state (IS), the YS (124.52 MPa) and UTS (145.26 MPa) of Cu/Al composite tube with 80%TR are improved by 58% and 10%, respectively. Cu and Al show ductile fracture and brittle fracture respectively, and more metastable critical cracks are excited at the interface to avoid debonding and delamination.