| As a"green engineering material for the 21st century",Mg and its alloys are widely used in all walks of life in society with their many advantages.However,due to its hexagonal close-packed crystal structure,Mg alloy has poor plastic deformation ability at room temperature.Studies have shown that pre-deformation is an effective way to improve the mechanical properties of Mg alloy.It can induce twins,change the grain orientation and refine the grains inside the Mg alloy.Pulse current has the characteristics of high efficiency and low energy consumption.It can heat the Mg alloy to a higher temperature in a very short time to finish the heat treatment process of the metal.Compared with the conventional heat treatment(CHT),electropulsing treatment(EPT)can completely restore and recrystallize the grains inside the Mg alloy at a lower temperature,eliminating the residual stress inside the metal.To apply pre-deformation to induce twins,changing the grain orientation inside the Mg alloy,and replace the CHT with EPT to complete the heat treatment process of the Mg alloy,can effectively eliminate the residual stress inside Mg alloy caused by the pre-deformation,accelerate the recovery and recrystallization,improve the performance of Mg alloy.In addition,the use of EPT technology to treat metals can not only save energy and improve energy efficiency,but also shorten production cycles and save human resources costs.Therefore,studying the effect of EPT on the microstructure and properties of pre-compressed AZ31B Mg alloys has theoretical significance and practical value for optimizing the plastic processing technology of Mg alloys and developing high-performance Mg alloys.Hot rolled AZ31B Mg alloy plate with a thickness of 5 mm was the material used in the study.The effect of EPT on the microstructure changes of pre-compressed Mg alloy plate was investigated first.Based on the quasi-static compression tests,the effect of EPT on the quasi-static compression behavior and anisotropy of the pre-compressed AZ31B Mg alloy was researched in detail.Using immersion hydrogen evolution test and electrochemical test,the effect of EPT on the corrosion resistance of AZ31B Mg alloy was also studied.The following conclusions are obtained through research:(1)EPT can heat the Mg alloy to a higher temperature in a very short time,making the pre-compressed Mg alloy undergoes complete recovery and recrystallization when EPT at 200?for 10 min to 15 min.(2)The flow stress change of the AZ31B alloy is insensitive to the static compression strain rate.And this was not changed by pre-compression deformation and EPT.When the AZ31B alloy is uniaxial compressed in the strain rate range of 1×10-4 s-1 to 1×10-2 s-1,the flow stress variation is about 10 MPa,which is within the error range.(3)EPT has a certain influence on the plastic deformation mechanism of AZ31B alloy.When the transverse direction(TD)pre-compressed AZ31B alloy plate is subjected to EPT at 200?for 10 min and 15 min,the deformation mechanism of AZ31B alloy is changed from twinning at the early stage,twinning and slipping interaction in the middle and late stages to the crystal slipping.(4)EPT can significantly reduce the anisotropy of AZ31B alloy on the ND-RD plane(perpendicular to the rolling surface of the plate and parallel to the rolling direction of the plate).For the normal direction(ND)pre-compressed AZ31B alloy plate subjected to the EPT process,the difference in yield strength(?YS)between the ND and RD samples of the alloy on the ND-RD plane is reduced to about 55 MPa.And for the TD pre-compressed AZ31B alloy plate subjected to the EPT process,the?YS of the ND and RD samples of the alloy on the ND-RD plane was reduced to about 15 MPa.Compared with the as-received AZ31B Mg plate's 87 MPa,the reduction was 36.8%and 82.7%,respectively.(5)It seems that pre-compression reduced the corrosion resistance of AZ31B Mg plate.The hydrogen evolution volume of the corrosion test samples at 0°,45°,and 90°was increased from 2 m L,2.3 m L,and 2.32 m L of as-received state to 2.45 m L,2.5 m L,and 2.4 m L of pre-compressed state,respectively.Compared with the as-received AZ31B plate corrosion test samples,the hydrogen evolution volume increased by 22.5%,8.7%,and 3.5%,respectively.The corrosion resistance of AZ31B plate was increased with the increase of EPT temperature.When EPT at 200?for 10 min,the hydrogen evolution volume of the corrosion test samples at 0°,45°and 90°were reduced to 1.8 m L,2.2 m L and 1.5 m L,respectively.Compared with those of as-received AZ31B plate,the hydrogen evolution volume was reduced by 10.0%,4.3%,and 35.3%respectively.In summary,the pre-compression of AZ31B alloy combined with EPT not only reduces the anisotropy of the plate in the ND-RD plane,but also helps to improve the corrosion resistance of the alloy. |
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