Adiabatic shear behaviors of cold-rolled pure copper under different deformation degrees

The hat-shaped specimens were prepared along the normal direction (ND) of the cold-rolled pure copper sheet. The dynamical shear test was conducted by the Split-Hopkinson pressure bar (SHPB). The adiabatic shear behaviors of cold rolled pure copper under different deformation degrees were systemically investigated by optical microscopy (OM), electron backscatter diffractometry (EBSD) and transmission electron microscopy (TEM). The results show that with the increase of strain rate, the peak stress and flow stress of corresponding to sample increase, and the strain rate hardening effect becomes more obvious. The adiabatic shear band (ASB) forms in the samples with different strains, and the change trend of the width of ASB is consistent. With the increase of strain, the strain gradient of transition region increases and ultrafine grains form within the ASB. The stable grain orientations, in which the crystal <110> direction tends to align with the local shear direction and the crystal {111} and {100} planes tend to parallel to the local shear plane, develop in the ASB areas. The thermodynamics and kinetics calculated results prove the possibility that the dynamic recrystallization can take place in shear bands based on the rotational dynamic recrystallization mechanism. Kinetic calculations indicate that ultrafine grains do not undergo significant growth during cooling stage after deformation. © 2021, Science Press. All right reserved.