Study On Texture Evolution And Strengthening Mechanism Of Multipass Power Spinning Of Tube Workpiece For AZ31B Magnesium Alloy

In recent years,with the development of trend to lighter weight,integration,higher performance and lower cost in the automotive,aerospace,and weaponry fields,stricter requirements are imposed on thin-walled tube workpieces.As one of the most effective methods for processing thin-walled tube workpieces,the power spinning has many advantages such as higher material utilization,lower cost,and better product performance.The increasing requirement for lightweight,energy efficiency and environmentally benign engineering is driving the widespread application of Mg alloy,who is not only the lightest structural metal,but also a recyclable material.However,the engineering application of magnesium alloys is still very limited to its low strength and poor plastic forming performance.At present,the research on the power spinning of magnesium alloy tube workpieces mainly focuses on the aspects of microstructure evolution,flaw controlling and dimension controlling.Tube workpieces formed by power spinning usually have anisotropy in mechanical properties,and the key of improving their service performance is how to improve their hoop performance.In this paper,AZ31 B magnesium alloy is used as the main research material,and the texture evolution and strengthening mechanism of AZ31 B magnesium alloy are carried out in this study.The cross spinning technique is used to control the microstructure and texture distribution of the tube workpieces to improve the hoop mechanical properties.The changes of microstructure,texture evolution and mechanical properties of AZ31 B magnesium alloy during spinning at low temperature and high temperature are respectively explored.The influence of the microstructure and texture of unidirectional spinning and cross spinning tube workpieces on its hoop mechanical properties is analyzed.The results show that,compared with unidirectional spinning,the cross spinning technique has a certain effect on the improvement of the hoop mechanical properties.However,as the temperature rises,the improvement is significantly reduced.Compared with unidirectional spinning,the hoop tensile strength of all samples of 3?6 pass cross spinning in low temperature increased by 8 MPa and the hoop tensile strength of all samples of 7?9 pass cross spinning in low temperature increased by 24.3 MPa.For the hoop mechanical properties of tube workpieces formed in high temperature,the hoop tensile strength of all samples of 3?6 pass cross spinning in high temperature increased by 7.6 MPa and the hoop tensile strength of all samples of 7?9 pass cross spinning in high temperature increased by 2.5 MPa.AZ31B magnesium alloy undergoes dynamic recrystallization during multi-pass unidirectional spinning and cross spinning.With the progress of spinning passes,that is,the increase in thinning rate,the grains of AZ31 B magnesium alloy are gradually refined.At the same time,the second phase deflects in the direction of RD with the flow of metal.With analysis of XRD results,it found that the texture has a small increase in the hoop tensile strength,and the strengthening is mainly affected by the grain refinement.The crystal plasticity model is used to calculate the strengthening effect of the spinning texture of AZ31 B magnesium alloy on the mechanical properties of the tube workpieces.The results show that the texture has a small effect on the hoop strength of the crosss pinning tube workpieces and also prove that grain refinement is the main strengthening factor.