Deformation behavior, microstructure and mechanical properties of pure copper subjected to tube hydroforming

In this study, the deformation behavior, microstructure and the mechanical properties of annealed pure copper through parallel double branched tube hydroforming were investigated. The deformation behavior was studied with hydroforming experiments along with the finite element method. Microstructure and mechanical properties investigations were performed with electron backscatter diffraction, transmission electron microscopy and hardness testing. The results indicated that the stress and strain distribution in the sample were inhomogeneous from region A to region B, during the parallel double branched tube hydroforming. The wall thickness decrease and increase at regions A and B were demonstrated, respectively. The microstructure characterization demonstrated that significant grain refinement could be obtained by the deformation-induced grain refinement mechanism. The grain size decreased and the fraction of low angle grain boundaries increased as the strain increased. The hardness presented a significant increase from the as-annealed sample to the as-deformed sample. Also, the hardness value at region B was almost twice the annealed copper hardness value during the calibration stage. Moreover, the hardness variation agreed with the microstructure changes.