Study On Cyclic Expansion-Extrusion And Precision Extrusion Vane Of Magnesium Alloy With High Strength And Toughness

This paper mainly studied the uniformity of the equivalent stress and strain,microstructure evolution,texture evolution and mechanical properties of AZ80 magnesium alloy during the deformation of cycle expansion-extrusion and use the billet through cyclic expansion-extrusion process as the billet of fine extrusion.The comparision of the microstructure and mechanical properties of the vane was conducted with that of traditional extrusion process.Firstly,the finite element analysis software wasused to simulate the uniformity of the equivalent strain and the stress of the cyclic expansion extrusion.Then,two kinds of processing schemes of AZ80 magnesium alloy were used to conduct the physical experiments of cycle expansion-extrusion deformation of each pass.The effects of different processing schemes and deformation passes on the microstructure evolution,texture evolution and mechanical properties of AZ80 magnesium alloy were analyzed,The comparision of the microstructure and mechanical properties of the vane of cyclic expansion-extrusion process was conducted with that of traditional extrusion process.the main conclusions are as followed:1.During the process of one-pass cyclic expansion-extrusion deformation,the maximum equivalent strain and the concentration ofstress at the specimen are both appearedin the shear deformation area,and the grainswerebroken and dynamic recrystallization occured.After multiple cyclic expansion-extrusion deformation,the equivalent strain of two schemes increased with the increase of the deformation pass,but the equivalent cumulative strain of the scheme oneperform larger and the strain showed good uniformity.The simulation results are in good agreement with the experimental results.2.The grain size of AZ80 magnesium alloy gradually decreased with the increase of the deformation pass,but the grain refining effect decreased with the increase of deformation pass.After one and two pass,the grain refinement wasobvious,however,after three and fourpasss,the refinement of the grain became inapparent.The grain refinementeffect of the scheme one was better than that of the scheme two,and the grainspeformed more uniform and equiaxed,and a large number of twins appeared in the plan two.3.During scheme one,the texture of the AZ80 magnesium alloy evolved from strong basal texture after one-pass to the texture contain low basal texture and cyclic expansion-extrusion deformation texture after four-pass.During schame two,the texture evolved from strong basal texture to low cyclic expansion-extrusion deformation texture.4.During scheme one,the hardness,tensile strength and yield strength of AZ80 magnesiun alloy with the increase of the deformation passes.But for schemetwo,the tensile strength and yield strength afterone-passreached the maximum value,after that,the tensile strength and yield strength are not increased withthe increase of the deformation pass.And the emergence of anti Hall-Petch theory phenomenonappeared,this is due to thesoftening effect of the texture during cycle expansion deformation process wasmore stengthing thanfine grain stengthing.5.Through scheme one,the blank had uniform microstructure and high mechanical properties,and its anisotropy was weak.Theblank after four-passes during scheme one was selected to form the vane and made comparision with that formed through traditional process.The results showed that the grains of the former were more refine and uniform,and the grains presented equiaxed.Simultaneously,its the anisotropy was weakened through the test of its mechanical properties.