Study On Deformation Mechanism,Microstructure And Properties Of AZ91D Magnesium Alloy By Electric Pulse Rolling

As one of the lightweight process materials in the new century,magnesium alloy has a wide application prospect in automobile,aerospace,communication and other fields.However,due to its poor deformation ability at room temperature,it is difficult to make large-scale industrial production by cold deformation methods such as cold rolling and cold stamping,which greatly limits the application of magnesium alloys in industry.In recent years,it has been found that the application of pulse current in the process of metal deformation can effectively improve its plastic forming ability.In this paper,strong pulse rolling technology was used to roll AZ91D magnesium alloy under four rolling conditions:cold rolling,electric pulse cold rolling,hot rolling and electric pulse hot rolling.The effect of electric pulse rolling on the microstructure and properties of AZ91D magnesium alloy was investigated.By changing the output voltage value,electric pulse rolling of AZ91D magnesium alloy was carried out at different output voltages to explore the effect of output voltage on the microstructure and properties of AZ91D magnesium alloy.The thermodynamic properties of Mg₁₇Al₁₂,mechanical properties of Mg and generalized layered fault energy of Mg before and after applying electric field were calculated by first principles method to explore the effect of external electric field on the deformation mechanism of AZ91D magnesium alloy.The findings:The electric pulse hot rolling process has the best rolling effect on AZ91D magnesium alloy.Theβ-Mg₁₇Al₁₂ phase changes from irregular bone shape to sheet shape,and the content ofβ-Mg₁₇Al₁₂ is reduced by～6.7%compared with the original sample.The mechanical properties of AZ91D magnesium alloy are the best.The microhardness ofβ-Mg₁₇Al₁₂ phase increases by 20%,the microhardness ofα-Mg matrix decreases by 15%,and the tensile strength of AZ91D magnesium alloy increases by 22%.With the increase of output voltage,the coarse and irregular skeletonβ-Mg₁₇Al₁₂ phase in the sample was transformed into small worm-like and lamellaeβ-Mg₁₇Al₁₂ phase.When the output voltage was 300V,the structure and properties were the best,the content ofβ-Mg₁₇Al₁₂ phase was the lowest,the texture strength was the lowest,and the content of twins was the highest.The microhardness ofβ-Mg₁₇Al₁₂ was increased by 20%,and the tensile strength of the samples was increased by 22%.When the electric field is applied,the Mg-Al bond of Mg₁₇Al₁₂ is easy to break,which makes it more easily dissociated in the matrix in the form of ions,and promotes the dissolution of Mg₁₇Al₁₂.The Poisson’s ratio of Mg increases when the electric field is applied,and the hardness of Mg decreases when the value of B/G is greater than 1.75.After applying electric field,the generalized fault energy of Mg base surface does not change much,and the generalized fault energy of Mg prism surface decreases significantly,and the plastic forming ability of Mg is improved after applying electric field.