Severe mechanical anisotropy of high-strength ultrafine grained Cu-Zn tubes processed by parallel tubular channel angular pressing (PTCAP)

Plastic anisotropy of ultrafine-grained (UFG) Cu-30%Zn tubes fabricated by parallel tubular channel angular pressing (PTCAP) process was investigated. The results showed that there was a severe anisotropy in UFG tubes in comparison with course grained counterparts. The PTCAP processed tube showed a very high strength of about 1220 MPa along the peripheral direction while it is about 580 MPa along the axial direction. Ultimate strength increased about 66% and 106% along the axial and peripheral directions, respectively. Comparison between the yield strength of CG and UFG tubes shows that the yield strength increases from ~106 MPa to ~344 MPa along the axial direction and ~359-1013 MPa along the peripheral direction. In the other word, the yield strength increases about 224% and 182% along the axial and peripheral directions, respectively. The hardness in the peripheral direction was almost greater than that in the axial direction which is in a good agreement with anisotropy of tensile properties. The corresponding textures verified this severe anisotropic in mechanical properties. The {111} plane was rotated about 90° with reorientation toward the radial direction after PTCAP processing while it is almost dispersal with a small texture to the extrusion direction in the annealed sample.