Study On Microstructure And Mechanical Properties Of AZ31B Magnesium Alloy Fabricated By Hot Spinning

Hot spinning is a kind of precise process,which is widely applied in aerospace,military industries and transportation,to manufacture rotary metal parts of high-performance.For the present paper,the multi-pass hot shear spinning of rolled AZ31B(Mg-3.0%Al-1.0%Zn-0.30%Mn)magnesium alloy and hot flow forming process of semi-continuous casting AZ31B tubes were conducted.And the influence of process parameters was investigated.The finite element model of AZ31B tubes fabricated by hot flow forming of single-pass was established to learn about the flow behavior,stress and strain distributions and the evolution mechanisms of microstructure and mechanical properties were obtained.For multi-pass shear forming of AZ31B rolled sheet,the obtained microstructure at different height is non-uniform.The microstructure near bottom is more refined and uniform.After shear forming,the difference of mechanical properties along rolled and tangential directions is nearly disappeared.When the spinning process is conducted with temperature of 340? and feed ratio of 1 mm/rev,the mechanical properties are better.Because of the axial compressive stress during shear forming,AZ31B magnesium alloy present(0001)plane parallel to rolled plane with some c-axes of grains deflecting to axial direction.AZ31B magnesium alloy has a good formability when processed by hot flow forming.The(1010)and(2110)planes of flow formed grains lie parallel to RD-AD plane with c-axes orientating to RD and deflecting to AD.The deflecting angle is minor near outer and inner surface and high in the middle region.When the process is conducted at the temperature of 420?,feed ratio of 0.1mm/rev and thickness reduction of 45%,AZ31B alloy tubes obtained refined and uniform microstructure with UTS of 280 MPa and YS of 175 MPa near the outer surface while 266 MPa and 153 MPa near the inner surface due to grain refinement and texture strengthen.During flow forming,materials suffer a tri-axial compressive stress and undergo compressive plastic strain in RD and tensile strains in the other directions.Discrepancies in the grain size along RD are influenced by the stress and strain rate distributions.The orientation of the first principal stress leads to a discrepancy of the grain orientations in RD.