| The plastic deformation ability of AZ31B magnesium alloy can be effectively improved by the asynchronous electric rolling process with tension,so that it can be rolled at a large reduction rate at low temperature.However,the influence of electric field,temperature field,stress-strain field and microstructure field on AZ31B magnesium alloy during asynchronous electric rolling is not clear.Therefore,aiming at this problem,the method of combining experiment and simulation is used to carry out multi-field coupling analysis,to find out the distribution law of each field,and to establish an electroplastic measurement and control system to realize the plasticization modification of ZA31B magnesium foil strip asynchronous electric continuous rolling process.Firstly,the electro-thermal coupling finite element model of asynchronous electric rolling is established.The influence of different current density,magnesium strip thickness,reduction rate and magnesium strip width on the distribution of electric field and temperature field is analyzed by the model.The results show that the electric field in the deformation zone gradually decays to 0 along the RD direction,and the maximum difference of the transverse current density of the electric field at the entrance is between 0and 2.5A/mm~2.The thickness has a significant effect on the peak temperature and inlet temperature of the magnesium strip during the electric rolling process.When the current density is 27.9A/mm~2,the thickness of the magnesium strip is reduced from 1 mm to 0.3mm,and the inlet temperature is reduced by about 100°C.When the width of the magnesium strip is in the range of 40～80 mm,with the increase of the width,the temperature at the entrance edge of the magnesium strip is gradually increased by the influence of the electric field distribution characteristics.Secondly,through the experiment of single-pass electric rolling stop,the influence of the electrothermal coupling field in the heating section on the microstructure field of the deformed magnesium strip was investigated.The results show that the initial recrystallization temperature of AZ31B magnesium strip in the heating section is 200°C.When the current density is 28.5A/mm~2,the recrystallization degree of magnesium strip reaches 94.4%at the entrance,the average grain size is about 4.61μm,the grain is refined and the plasticity is improved.The uniform electro-thermal coupling field of the heating section makes the grain size of the magnesium strip inlet with a width below 80mm uniformly distributed along the transverse direction.Finally,the multi-pass electric rolling experiment of AZ31B magnesium foil was carried out by using the designed strip asynchronous electric rolling experimental platform.The results show that by controlling the current density at 28.5A/mm~2 and the tensile stress at 30MPa to rolling the magnesium strip,the rolled magnesium strip is flat and the surface quality is good.Finally,the very thin magnesium foil with a thickness of 0.077mm was successfully prepared within 9 passes without intermediate annealing.According to the electric rolling process,the electroplastic rolling measurement and control system is compiled.The system can accurately calculate the electrothermal coupling in the process of strip asynchronous electric rolling,and can be adjusted in time,which provides an effective control method for the plasticization and modification of wide magnesium strip.The research on the multi-field coupling law in the process of asynchronous electro-rolling provides an important reference for the plasticizing modification of AZ31B magnesium alloy and the mass production of wide magnesium foil. |
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