Deformation Mechanisms Of Magnesium Alloy AZ31 Under Pulsed Electric Current

As the lightest structural metallic materials,Magnesium(Mg)alloys have long been regarded as competitive candidates in the weight-critical fields such as airospace,automobile and electronic industry.Unfortunately,due to its poor room temperature formability and thus the high production cost,the large-scale application of the material is still rather limited these days.The formability of the alloy is known to be closely related to its texture.Research has shown that by some intelligent processing methods or through alloy design using rare earth(RE)elements,the texture of Mg alloys can be largely modified,which benefits the subsequent fabrication processes.However,the equipment complexity and the high cost of RE elements hinders these two solutions from becoming the optimum choices in commercial applications.In this research,pulsed electric current was employed to assist the fabrication of Mg sheet AZ31.The possibilities of modifying the microstructure and texture of AZ31 using pulsed electric current were investigated.Techqniques such as electron backscattered diffraction(EBSD)and viscoplastic self-consistent(VPSC)modeling have been used to analyze the microstructure and texture evolution.The emphasis was placed on the influence of the electric current on the deformation and recrystallization processes.Firstly,AZ31 sheets were subjected to single-pass and small-reduction electroplastic rolling and conventional warm rolling.By comparing the twinning behaviors of the alloy under the two regimes,the influence of the pulsed electric current on the twinning behavior(twinning type,twinning fraction and twinning variant selection)was revealed.Secondly,the microstructure and texture evolution of AZ31 sheet during multipass and small-reduction electroplastic rolling and conventional warm rolling were systematically studied.The enhanced rollability of the alloy when it was rolled assisted by pulsed electric current was explained from the perspective of twinning,shear banding and the occurance dynamic recrystallization(DRX).Thirdly,large strain electroplastic rolling was conducted on AZ31 sheet with the assistance of pulsed electric current with a series of current densites.The as-rolled microstructure and texture were characterized.Based on these informations,the influences of the pulsed electric current on the deformation and DRX mechanisms were discussed.The contributions from deformed matrix and DRX grains to the overall texture were evaluated.Finally,the microstructure and texture evolution of pre-rolled AZ31 sheet during electropulse treatment were studied.The effect of the pulsed electric current on the nucleation and nuclei growth of the static recrystallization were explained.This research shows that pulsed electric current can be employed as an effective tool to modify the microstructure and texture of Mg alloy AZ31.The results could be able to serve as guidance for the future application of the pulsed electric current on Mg alloy fabrication in industry.