The Application Of "Electroplastic Effect" In Wire-Drawing Process And Analysis On Its Mechanism

In this paper, the effect of current pulses on the properties of materials, such as mechanical property, microstructure, and electronic and magnetic properties has been discussed. Materials used in this experiment are 1Cr18Ni9, 17-6Mn and 4J42 alloys. The wire-drawing equipment was self-designed and produced. The current pulse trigger controlled by a CPU can generate current pulses with frequency between 0~1000Hz, and the density of the current pulses is about 103~105A/cm2 with duration of about 20ms. It has been found that with the introduction of current pulses, the drawing stress will be greatly decreased. Some times the amount of decrease can be up to 50%. And the plasticity of materials can be significantly improved. Namely, the limited strength sb was decreased and the elongation d(%) was increased, which is just the nature of the so-called "Electroplastic Effect". With the analysis by Scanning Electron Microscope (SEM), it is found that the surface quality of the wire drawn with current pulses is smoother than that drawn by conventional wire-drawing process. Simultaneously, the crystal size of the wire drawn with current pulses is smaller and more even comparing with the wire drawn without the introduction of current pulses. Tremendous plates of Austenite twins and some train-induced Martensite were found in the wire drawn with conventional process by the Transmission Electron Microscope (TEM). However, in the wire drawing with current pulses, the amount of plates is not that much. And generally speaking, the Martensite induced by plastic deformation is found to be very scare in the materials treated with current pulses by X-Rays detection. The electronic and magnetic properties have been greatly affected by the current pulses, too. The resistivity of materials drawn with current pulses was about 10% lower than that of wire drawn without current pulses. The saturated magnetization Bs and residual magnetization Br of wire drawn with current pulses was about 2 orders lower than those of the wire drawn without current pulses. Because martensite is ferromagnetic phase and Austenite is paramagnetic phase; hence,the retardation of strain induced matensite will lead to the decrease of magnetization of materials. This result is consistent with the analysis by TEM. As concern to the Coercive Force. Hc, with the introduction of current pulses, the value of Hc was increased with the accruement of deformation, on the contrary, without the excitation of current pulses, the value of Hc was decreased with the accruement of deformation.