Особенности пластической деформации ультрамелкозернистой меди при разных температурах

An electron-microscopy examination of microstructure evolution in ultrafine-grained copper specimens under active tensile loading is carried out at T = 293 and 452 K. At T = 293 K, the formation of strain-localization mesobands via quasiperiodic generation and relaxation of stress concentrators in the front of propagation of these mesobands is shown to be a most important mechanism of plastic flow since the onset of deformation. Special features of the crystal geometry of reorientation and fine defect substructure in the zone of generation and relaxation of stress mesoconcentrators are studied. Local internal stress fields in these zones are evaluated. The mechanisms of plastic relaxation of stress mesoconcentrators in the mesoband propagation front are revealed and discussed: dynamic recrystallization, mechanical twinning, and dislocational-disclinational deformation mechanisms. It is demonstrated that an appreciable increase in plasticity of ultrafine-grained copper with increasing deformation temperature is a consequence of a decrease in its scale level (from meso to micro) resulting from structural instability of the ultrafine-grained state and rapid development of dynamic recrystallization throughout the specimens.