Research Of The Deformation Behavior,Texture And Microstructure Evolution Induced By Electropulsing In Al And Mg Alloys

In response to the trend of light weight in industrial manufacturing,light alloys represented by aluminum alloy and aluminum alloy have been widely concerned and applied.However,magnesium is HCP structure,and its strong basal texture leads to poor room temperature plasticity,which is the bottleneck in processing and application of deformed magnesium alloys.Although the plasticity of aluminum alloy is better than that of magnesium alloy,the existence of Lüders bands and anisotropy have adverse effects on its plastic deformation ability.In industrial production,hot forming is usually used to improve the plastic deformation ability of aluminum and magnesium alloys.In this way,the dimensional precision and surface quality of the formed parts can be ensured.Electroplasticity effect refers to the phenomenon that the flow stress decreases and the plastic deformation ability increases under the action of the current.In recent years,electroplasticity has been applied in the processing and forming of materials,which is called electrically-assisted forming.Therefore,the study on the electroplasticity effect of aluminum and magnesium alloy has a good practical application prospect,and can also supplement and perfect the mechanism of electroplasticity effect.This paper chosen the low-frequency pulsed current,which is low energy consumption and suitable for industrial production.5052 aluminum alloy and AZ31 magnesium were used to carry out electropulsing tension tests.Then the microstructure and texture evolution under the action of pulsed current were characterized and analyzed by XRD,EBSD and TEM.Moreover,the electropulsing tension with forced air-cooling was carried out to explore the mechanism of the thermal and electromigration effect,achieved the following results:1)Appropriate pulsed current parameters can promote the dynamic recrystallization of 5052 aluminum alloy,improve its plasticity and inhibit the PLC effect.When the effective current density was 16.8 A/mm2,the dislocation density in the material significantly decreased,the recrystallization degree increased,and the elongation of the material after fracture increased from 9.2 % to 24 %.2)With the increase of effective current density from 9.7 A/mm2 to 16.8 A/mm2,the deformation texture in 5052 aluminum alloy gradually changed to recrystallization Cube texture.Since the misorientation between S texture and Cube texture is 40°<111>,the transformation from S texture to Cube texture is particularly obvious.Since the schmid factor of Cube texture is greater than that of S texture and Brass texture,the stronger Cube texture improved the plastic deformation ability during the electropulsing tension.3)Different from aluminum alloy,AZ31 magnesium alloy showed the strongest electroplasticity effect when the effective current density was 8 A/mm2,and the elongation after fracture increased from 24.7% to 38.08%.The TEM results showed that it was due to the promoting effect of pulsed current on the dynamic recrystallization of magnesium alloy.4)The thermal effect of the pulsed current promotes the dynamic recrystallization,leading to weakening of the basal texture,and activation of the base slip {0001}<2-1-10> and {2-1-10}<10-10> prismatic slip,in which {2-1-10}< 2-1-10> prismatic slip is <c> slip,which can coordinate the deformation of magnesium alloy on the c axis,so the plasticity of magnesium alloy was improved.5)During the electropulsing tension with forced air-cooling,the thermal effect was weakened and the degree of recrystallization of the material was also inhibited,which manifested as the weakening of the electroplasticity effect macroscopically.The calculational results show that it is inappropriate to ignore the athermal effect and regard the electropulsing tension deformation as the pure thermal deformation.Under the low-frequency pulsed current used in this study,the thermal effect and electromigration effect dominate the nucleation and growth of recrystallization respectively.It is different from the previous research results under high-frequency pulsed current.