Mechanical properties and fracture behavior in copper-brass heterostructured fibers

Inspired by natural structures like bamboo and bone, the incorporation of heterogeneous fibrous structure plays a significant role in skillfully optimizing their mechanical properties. A set of copper-brass heterostructured fibers has been successfully designed and fabricated by a novel strategy, named DRA (diffusion welding, rotary swaging and annealing). This leads to a significant improvement in the synergy between strength and ductility, which can be attributed to the HDI (hetero-deformation induced) hardening effect caused by the high density of heterointerfaces. The experimental results found that once the GND (geometrically necessary dislocations) density around the hetero-interface reaches the saturation, some GNDs can spread into the adjacent copper and brass zones to alleviate partial stress concentration. The presence of four-sides interfaces in the fibrous composite restricts the dislocation storage capacity of individual fiber, thereby abundant GNDs accumulating near the hetero-interface to produce significant stress concentration and HDI stress. Simultaneously, the severe stress concentration promotes the initiation and propagation of micro-cracks at the hetero-interfaces. These results lead to a more significant HDI hardening while a faster decrease in the work hardening rate of the hetero-fiber during the later stage of tension. Our findings have significantly enhanced our understanding of the deformation mechanism of heterostructured materials. Additionally, this innovative structural design strategy has proven to be highly valuable in the development of heterostructured materials with substantial potential for various applications.