Study On Isothermal Extrusion Forming,Interfacial Microstructure Evolution And Mechanical Properties Of Al-Mg Bimetals

With the development of science and technology,structural lightweight design technology has been paid more and more attention,and has great prospects for development.Among them,aluminum and magnesium are both lightweight materials,which are favored in structural lightweight design technology and environmental protection issues.Magnesium alloys are easy to be corroded,which greatly limits their application range.A dense oxide film can be formed on the surface of aluminium and aluminium alloys,which makes them have better corrosion resistance.In this paper,a layer of aluminium or aluminium alloy is coated on theoutersurfaceofmagnesiumalloysbyisothermalextrusiontoprepare magnesium-aluminium composites with excellent corrosion resistance.In this paper,the rigid-plastic finite element method and Deform-3D software are used to establish the finite element model of Al/Mg bimetallic isothermal extrusion.The metal flow rule,equivalent plastic stress,equivalent plastic strain and temperature field distribution of AA6060 aluminum alloy and AZ31 magnesium alloy during isothermal extrusion are discussed.The effects of extrusion temperature,extrusion speed,die angle and billet geometry on forming load were studied by orthogonal experiment,and the optimum process parameters were obtained.Combining with the actual production and other complex conditions,the optimal experimental parameters are obtained as follows:extrusion speed 2 mm/s,aluminium billet size?10mm×20mm,magnesium core size?5mm×19mm,extrusion temperature 360?and extrusion die angle 90°.The bonding interface of the extruded products was evaluated.Microstructure and chemical composition of Al-Mg interface were analyzed by optical microscopy?OM?,scanning electron microscopy?SEM?,energy dispersive spectroscopy?EDS?and electron backscatter diffraction?EBSD?,and mechanical properties of the interface were evaluated by shear test and microhardness test.The results show that during isothermal extrusion of Al-Mg bimetals,Al-Mg elements diffuse to form Al-Mg intermetallic compounds,Al₃Mg₂ phase is formed on the Al side,Al₁₂Mg₁₇7 phase is formed on the Mg side,and the total thickness of the bonding layer is about 4?m.In the isothermal extrusion process,recrystallization occurs in both the outer aluminum alloy and the inner magnesium alloy,which leads to the growth of grains in varying degrees.There are strong{011}<211>brass texture and{112}<111>copper texture in the extrusion process of aluminium alloy.In the extrusion process,there is a strong plane texture?0001?parallel to ED,and the main texture is{01-10}<0001>and{12-10}<0001>.The shear forces acting on the interface are different,and most of the failure occurs abruptly without plastic deformation.The maximum shear strength of the interface is 56.29 MPa and the minimum shear strength is 39.88 MPa.The hardness of the bonding zone is obviously higher than that of the matrix on both sides due to the formation of Mg-Al intermetallic compounds,and the hardness value reaches 169.6HV.