材料期刊网

The microstructure of the Cu-Ni alloy specimen ER is mainly elongated coarse grains. However, the microstructure of the specimen EH is inhomogeneous and some recrystallized sub-grains form. In addition, the misorientation angles of the specimens ER and EH are mainly smaller than 15 degrees, showing a feature of low-angle grain boundaries. Although the uniform elongation of the ECAPed Cu-Ni alloy decreases rapidly, the yield strength of the Cu-Ni alloy is improved more than three times after ECAP for one pass. The mechanical properties, deformation, and fracture of Cu-Ni alloy are not significantly affected by the strain rates. With the increase in strain rates, the yield strength of the specimen E0 hardly changes but the ultimate tensile strength increases slightly. However, with the increase in strain rates, the tensile strength of the specimen EH gradually improved. Besides, the fracture fractographies of the specimens EH turn into shear dimples at high strain rate. In addition, both the strain-hardening exponent n and strain-rate sensitivity m of the specimens EH are small, inducing lower strain-hardening, uniform plastic deformation and resistance to the shear deformation.