| Materials'superplasticity will be improved in electric field. It has an important value and prospects for industrial applications that combining the electrosuperplasticity of materials with solid-state welding technology to develop new technology of solid-state welding. In this paper, we designed and produced a set of electrosuperplastic compression and solid-state welding experimental devices which can provide an electric field environment. Based on this, materials'compression superplasticity was studied, and a new technology of solid-state welding was developed.The experimental device mainly consists of four systems: the high-voltage power supply system, the applied electric field devices for making the sample in electric field, the heating and temperature control system, and the loading and data acquisition system. The device can provide the electric field of DC, AC and pulse at the specimen surface, and has 12 kinds connection between the specimen and the ring electrodes in a total. The electric field strength ranges from 0 to 15kV/cm, working temperature ranges from room temperature to 950℃, pressure testing machine head speed ranges from 0.02 to 60mm/min. The electric field strength at specimen surface is uniform, and the electrode, specimen and the test machine are insulated each other. The entire process of electrosuperplastic compression deformation is monitored, and the datas are recorded, analyzed and displayed by the computer.The 40Cr steel and 1.6%C ultra-high carbon steel(UHCS-1.6C) were objected in this paper. Mechanical characteristics of UHCS-1.6C with spheroidizing annealing superplastic deformation were measured, and superplastic solid-state welding tests of UHCS-1.6C/40Cr were made in the self-made device. The influences of electric field and other process conditions on the mechanical characteristics of superplastic compression of UHCS and welded joints of UHCS-1.6C/40Cr were investigated. The mechanism of effect of electric field on the superplasticity of UHCS-1.6C and solid welded joint formation mechanism of UHCS-1.6C/40Cr were researched. The results showed that, UHCS-1.6C presented good electro-superplastic compression superplasticity at the temperature of 760~780℃and the initial strain rate of (0.75-3.0)×10-4s-1. The applied electric field dropped the steady-state flow stress of UHCS-1.6C no manner the specimen connected to positive or negative terminal at the temperature of 780℃and initial strain rate of 1.5×10-4s-1. While the electric field effect is more prominent when the specimen was connected to the positive, the steady superplastic flow stress maximumly decreased 10.5% and the strain rate sensitivity rised to 0.46 from 0.28 at the temperature of 780℃and the electric field strength of 3kV/cm. At the same time external electric field was also significantly reduced the deformation activation energy UHCS-1.6C during the superplastic flowing.There was no new phase appearing after compression in UHCS-1.6C, and the electric field was propitious to maintain equiaxed grain, and this effect is mainly manifested in the sample marginal zone. The joint strength of loop quenched 40Cr to spheroidization annealed UHCS-1.6C was 533MPa, with the holding temperature time of 20min, the pre-compressive stress of 56.6MPa, the initial strain rate of 1.5×10-4s-1, welding temperature of 780℃, electric field strength 3kV/cm and welding time of 8min, which was close to 76% of the base material strength of 40Cr and higher by 15% than the welding joint under the same conditions but without the electric field.The large number of superplastricity and solid-state welding tests made with this device show that: this set of device was full-featured and high testing accuracy, solved the insulation problem at the cases of high-temperature, high-voltage and dynamic load. This device is safe and reliable, easy to operate, and can meet research requirements of superplastic compression properties of solid materials and superplastic solid-welding technology in strong electric field.
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