Study On Interface Composite Mechanism Of Al/Mg Bimetallic Laminated Extrusion Cabin Section

Aiming at the lightweight requirements of high-end equipment,the design method of aluminum-magnesium bimetallic laminated cabin is proposed,which combines the excellent properties of magnesium alloy and aluminum alloy,obtains better specific strength,and solves the key problems of low elastic modulus and poor corrosion resistance of magnesium alloy.Interface control is a key factor in the preparation of aluminum-magnesium laminated materials,which has been paid attention to by researchers.However,for a long time,the mechanism of aluminum-magnesium interface composite and the key factors affecting the interface have become a research problem,which has not been solved.Based on this,this paper first designs the aluminum-magnesium bimetallic cabin structure to determine the interface strength that meets the service conditions,and then uses the cohesive force model as a bridge to establish a cross-scale simulation from micro to mesoscopic.Finally,the experimental method is used to verify the system.The aluminum-magnesium bimetallic laminated interface composite mechanism.The main conclusions are as follows:（1）The material is Mg-9Gd-4Y-2Zn-0.5Zr rare earth magnesium alloy and 2A12 aluminum alloy.The aluminum-magnesium bimetallic cabin structure was designed.The thickness ratio of the three-layer Al/Mg/Al structure was determined to be 1:3:1 with the design goal of reducing weight by 15%.The finite element software ANSYS static simulation was used to check that the interface strength was greater than 45 Mpa to meet the service conditions.（2）The influence of process factors on the macroscopic law and microscopic mechanism of interfacial diffusion behavior during extrusion process was studied by molecular dynamics method.The results show that in the range of 100Mpa-300Mpa,increasing the deformation temperature and reducing the extrusion rate can promote the mutual diffusion between aluminum and magnesium atoms.（3）When the thickness of the intermetallic compound interface layer is 3.2nm,the interface strength meets the service conditions,and the interface elastic modulus is the best,which is51Mpa.According to the MD simulation data,the cohesive model parameters of the Al/Mg interface under vertical load loading conditions were fitted.（4）The macroscopic simulation model of Al/Mg bimetal extrusion composite was established,and the macroscopic thermal evolution law in the extrusion composite process was analyzed to reveal the extrusion composite connection mechanism.A three-dimensional thermal-mechanical coupled finite element model was constructed to explore the evolution of temperature and stress during extrusion.Through the analysis of stress field and temperature field,the maximum temperature of the interface is lower than the melting point of the base metal,and the maximum temperature is 480°C.The contact stress between the two metals during extrusion is between 100Mpa-300Mpa.The process parameters were determined as temperature 440°C and punch reduction rate 1mm/s.（5）Through the push-ring experiment,the interface shear strength reaches 70Mpa,the interface hardness is 129HB,which is higher than 75Mpa of the aluminum layer and 105Mpa of the magnesium layer,which proves that the aluminum-magnesium bimetallic interface has been effectively combined.The microstructure was observed by optical microscope and scanning electron microscope.An interface layer with an average thickness of about 9.5μm was formed at the bonding interface.The element content in the interface and matrix was measured by EDS line scanning and surface scanning.It was speculated that three intermetallic compounds were formed at the interface,namely Al₁₂Mg₁₇,Al₃Mg₂ and Mg-Gd phases,which made the Al/Mg alloy achieve metallurgical bonding.It is speculated that the Mg-Gd phase is the main reason for improving the interface strength.Finally,the aluminum-magnesium bimetallic laminated cabin was successfully prepared by WCE process.（6）Through comprehensive analysis of physical experiments,macro and micro simulations,it is concluded that the mechanism of interface bonding of Al/Mg bimetal extrusion composite can be summarized as the result of the combined effect of plastic deformation of the material in the micro area of the interface,the formation of the interface diffusion layer and the combination of aluminum and magnesium metallurgy.