Study On Electro-Plastic Effect Of Copper And Copper Alloy Under Electric Pulse Effect

The electro-plastic effect refers to the interaction between electrons and dislocations under the influence of moving electrons,which is characterized by a sharp decrease in deformation resistance and a significant increase in plasticity.Based on this phenomenon,the electro-plastic processing can be used to reduce material deformation resistance,meanwhile improve the plastic deformation capacity of materials.Therefore,it has a good industrial application prospect,especially for the forming of intractable metal.However,the cause of Electro-plastic effect is still unclear,its influence factor and physical mechanism are still lack of systematic research too.In this thesis,scanning electron microscopy(SEM-EBSD)and transmission electron microscopy(TEM)technique were used to analyze the electro-plasticity effect and microstructure evolution of H62 brass and copper.The effects of tensile strain rate and pulse current density on the electrical plasticity were studied.The stress-strain and microstructure evolution of H62 brass and copper were coMPared during the drawing process under two processing conditions,one is under the different pulse current conditions and the other is under constant temperature conditions.Further investigation has reinforced the understanding of mechanism for pulse current processing,thus promoting the development of pulse current processing technology.By applying different pulse current densities(4.4A/mm2、6.7A/mm2、8.9A/mm2、11.1A/mm2、13.3A/mm2、15.6A/mm2、17.8A/mm2 and 20.0A/mm2)and tensile strain rates(2×10-4s-1 and 1×10-3s-1),the electro-plastic effect of H62 brass and pure copper were investigated,following conclusions can be drawn:the electro-plastic effect of H62 brass has improved markedly at the strain rate of 2×10-4s-1,pulse current density ranging from 6.7 to 13.3A/mm2,which also shows higher plasticity coMPared with processing conditions without pulse current.Further observation of the dislocation patterns and microstructure reveals that within the range of pulse currents can promote dislocation motion,facilitate dislocation tangle segregation and enhance the recrystallization of H62 brass at lower temperature.Meanwhile the plasticity decreases in the range of 17.8-20.0A/mm2,in this case the high pulse current density and concurrent Joule heating promote formation of twins,leading to higher twins content than samples under other pulse current conditions.At a strain rate of 1×10-s-1,the electro-plastic effect of H62 brass and copper samples is minor.The electro-plastic effect of copper is obvious at the strain rate of 2×10-4s-1,the pluse current density of 20.0A/mm2.