Research On The Integration Process Of Aluminum-Clad Magnesium Laminated Sheet Forming And Composite

Magnesium alloy materials have the advantages of low density,high specific strength and superior shock absorption performance.In the current material light-weighting requirements,if the magnesium alloy is fabricated into a thin-walled member,the material and structure can be lightened twice.However,due to its poor room temperature forming ability and poor corrosion resistance,its application is greatly hindered.Considering that the 5XXX series aluminum alloy（Al-Mg system）has good formability and corrosion resistance,it is good to combine the advantages of the two alloys by laminating the aluminum alloy sheets on both sides of the magnesium alloy.However,in practical applications,it has been found that aluminum-clad laminates prepared by various processes have new hard and brittle phases,which have a great influence on the properties of the sheets,especially in the secondary forming process.Therefore,this paper aims to explore that the 5052/AZ31B/5052laminated thin-walled members can simultaneously achieve diffusion bonding of magnesium alloy sheets and aluminum alloy sheets during hot forming（bending or solid particulate media drawing and bulging）,which can effectively avoid lamination.The problem of secondary forming cracking of the board realizes the integration process of preparation and forming of the 5052/AZ31B/5052laminated sheet,and provides technical support for the application and promotion of the laminated sheet.In this paper,5052/AZ31B/5052 laminated sheets with different thickness matching methods were prepared by hot pressing at 400°C,20 MPa and 2 h.The microstructure and mechanical properties of the laminated plates were studied.The laminated plates form a uniform linear diffusion layer at the interface junction.After analyzing the microstructure of the magnesium alloy in the core of the laminated plate,it was found that the grain size of the magnesium alloy did not change significantly before and after hot pressing,and all of them were fine and uniform equiaxed crystals.The microstructure of the diffusion layer at the interface of the laminate was analyzed.It was found that the diffusion layer consisted of the Mg₁₇Al₁₂2 phase near the AZ31B magnesium alloy sheet and the Al₃Mg₂ phase near the 5052 aluminum alloy sheet.The ratio of the thickness of the two phases was about 1:3,and the thickness of the laminate diffusion layer of different thickness matching methods is approximately equal.In order to analyze the comprehensive mechanical properties of the laminated sheets,the uniaxial tensile and bending tests were carried out on the laminated sheets of different thickness matching methods.By analyzing the uniaxial tensile test of laminated sheets with different matching methods at room temperature and high temperature,it is found that the tensile strength of the laminated sheet decreases with the increase of temperature,and the elongation increases with the laminated sheet.With the increase of the thickness of the laminated sheet,the tensile strength of the laminated sheet also shows a downward trend,and the laminated sheet with the thickness matching mode of 1（5052）+1（AZ31B）+1（5052）mm is superior.The tensile strength at room temperature is 232.99 MPa and the elongation is 13.8%.When the temperature is higher than 200℃,the elongation can reach 40%or more;the bending test of the laminated sheet is performed,and the bending property of the laminated sheet with the thickness matching method of 1（5052）+1（AZ31B）+1（5052）mm is also better,the maximum deflection is 25 mm.The interface analysis of the tensile and bending specimens shows that the Al₃Mg₂ phase near the 5052aluminum alloy sheet is an easy-to-failure zone,and cracking occurs first during the deformation process.Through the study of the microstructure and properties of the laminated sheet,it is found that the laminated sheet prepared by 1mm AZ31B magnesium alloy and 1mm aluminum alloy has the best performance.Therefore,the composite forming integrated laminated sheet member is prepared by different forming processes under the thickness matching mode.Metallurgical bonding occurs at the interface of the bend-formed-diffused composite integrated V-shaped laminated sheet member prepared by T=400°C,P=5 MPa,10 MPa,and holding pressure for 2 h,and the surface quality is superior,with the increase of pressure and bending angle,the thinning rate of the core magnesium alloy layer compared with the aluminum alloy layer is larger,and the laminated sheet as a whole has a thinning tendency;The appearance of the truncated cone-shaped laminated sheet member prepared by the integrated process of drawing and bulging（T=450°C）-diffusion bonding（T=400°C,F=400 kN heat preservation,holding pressure for 2 h）is good.A diffusion layer having a thickness of about 30μm was formed at the interface of the layer interface,but there was no interlayer peeling and cracking.The above experimental conclusions can provide a technical basis for the production and preparation of the aluminum-clad magnesium laminated sheet integrated components.