Study On Anisotropic Electroplastic Constitutive And Electro-rolling Process Of AZ31B Magnesium Alloy

Magnesium alloys tend to form a large number of twins and severe basal surface texture during the rolling process below the recrystallization temperature,which leads to its strong mechanical anisotropy,and even fractures and deformation mechanisms occur during the complicated rolling processing.Compared with the traditional magnesium alloy processing technology,the pulsed current can reduce the metal's resistance to deformation,improve its mechanical properties and surface quality effectively,and is suitable for difficult-to-deform metal especially.In this paper,starting from the anisotropy and microdeformation mechanism of magnesium alloy rolling,we explore the rolling process of magnesium alloy electroplastic foil strip.First,based on uniaxial tensile tests under different conditions,the influence of electric pulse parameters on the mechanical properties of pre-rolled magnesium alloys in different directions was studied.At 100??250?,compared with isothermal stretching in the RDTD plane,the flow stress difference in different directions first increases and then decreases with the increase of equivalent current density.The threshold of non-thermal effect appears at 175?.And the non-thermal effect of the pulse current is more obvious at high peak current density;the electroplastic effect is more obvious at low temperature,the degree of microstructure recrystallization is higher,and the crystal grains are finer;the electric pulse only improves the anisotropy at high peak current density The degree is slightly stronger than the results of the no-current test.At the same time,based on the experimental results,the anisotropic constitutive model of magnesium alloy under the action of electric pulse is established based on the Johnson-Cook constitutive model.Secondly,through the static electric pulse treatment experiment on the magnesium alloy strip,the distribution law of the temperature field generated by the electric pulse is proved.In the experiment,the loading method of the electrode has a great influence on the temperature field of the magnesium alloy,and the peak value of the temperature field always appears at the electrode loading place.At the same time,the pulse width of the pulsed electricity has a greater influence on the temperature of the sample than the pulse frequency;the equivalent current density is obtained based on Joule's heat law as a function of the average temperature of the sample surface,which can better reflect the magnesium alloy under pulsed current The temperature change situation.Based on the experimental results,the electrode loading method was optimized.Finally,based on the designed electric pulse rolling experiment platform,single-pass and multi-pass electric pulse rolling experiments were carried out.The influence of electric pulses on magnesium alloys with different deformations was proved,and the feasibility of continuous thermal-free electric rolling was verified.Under low deformation,excessive pulse current will increase the mechanical anisotropy of magnesium alloy after rolling.The deformation mechanism is twinning and grain boundary migration to compete and coordinate deformation;when the deformation is 14% to 17%,the pulse Current induced dynamic recrystallization,which can effectively reduce the anisotropy after rolling.Finally,multi-pass electric pulse rolling without intermediate annealing was realized,and the0.13 mm magnesium alloy foil was successfully prepared.