Research On Microstructure And Mechanical Properties Of AZ31B Magnesium Alloy Processed By Hot Shear Spinning

Shear spinning is an effective manufacturing method for the production of high-precision thin-walled rotationally components.Because of simple equipment,low forming forces and high precision,spinning process has been employed widely to produce structural components in automotive and aerospace industries.For the present paper,the finite element model of hot shear spinning was established to learn about the flow behavior,stress and strain distributions and optimize the process parameters.The hot shear spinning and differential temperature shear spinning of rolled AZ31 B magnesium alloy were conducted.Microstructure and mechanical properties were studied under different parameters including temperatures,spindle speeds.Furthermore,the texture of hot shear spinning and the effect of texture on mechanical properties were analyzed.The simulation results show that the principal stress in the deformation zone of shear spinning is compressive stress,and the minimum principal stress is perpendicular to the surface of the workpiece.Under the minimum principal stress,the materials flow along the wall thickness direction.The materials surffer tensile strain and compressive strain along the workpiece generatrix and wall thickness,respectively.Dynamic recrystallization occurs during hot spinning of AZ31 B magnesium alloy.As the deformation temperature and feed rate increase,the grain size increases,but the grain size decreases slightly with the spindle speed increasing.Due to the minimum principal stress in the deformation zone,the strength of the basal texture is increased after shear spinning.When shear spinning is carried out under a temperature of 200°C,a spindle speed of 300 rev/min and feed ratio of 0.1 mm/rev,the optimal mechanical properties can be obtained: the yield strength(YS),ultimate tensile strength(UTS)and elongation reache 202 MPa,280 MPa and 12.4% along Rolling direction(RD)while these reach 228 MPa,284 MPa and 11.4% along Transverse direction(TD),respectively.The spinning temperature has a significant effect on the microstructure of the workpiece during differential temperature shear spinning.Numerous twins and fine recrystallized grains appear in the microstructure when deformed at 150°C,while full dynamic recrystallization occurs at 250°C.The circumferential microstructure of the workpiece is uniform,but that for the wall thickness direction and the axial direction is uneven.When the shear spinning is carried out under a temperature of 200°C,a spindle speed of 600 rev/min and feed ratio of 0.1 mm/rev,the optimal mechanical properties can be obtained: the YS,UTS and elongation reache 251 MPa,304 MPa and 21.1% along RD while these reach 239 MPa,299 MPa and 21.8% along TD,respectively.And the sheet deformed at 150°C obtaines higher strength: the YS along RD and TD directions reaches 309 MPa and 293 MPa,meanwhile the UTS along RD and TD reaches 351 MPa and 333 MPa.