Formability Behavior of the Ultrafine Grained Thin-Walled Tubes During Square-Sectional Hydroforming Process

In the present study, formability of the ultrafine grained (UFG) Cu–Zn tubes were investigated during hydroforming process. The coarse-grained brass tubes were processed by the parallel tubular channel angular pressing (PTCAP) resulting in significant grain refinement. Then, coarse grained and UFG tubes were processed in a square-sectional hydroforming die. The results showed that the UFG tubes due to the lower formability and higher strength had a larger corner radius which was 6.35 mm while it was 1.9 mm for the annealed tube which is in good agreement with the tensile test data. Thickness distribution of the tubes were also examined through FEM simulation, and it was compared with the experimental data. SEM micrography was applied to evaluate fracture surface of the tubes after bursting.