Study On The Structure And Properties Of Al/Mg/Al Laminated Sheets With Different Thickness Ratio

The Metal laminated composite plate can give full play to the performance of each component plate,and has become a hot spot for research.As the lightest structural material and its own advantages,magnesium alloy has a very broad application area,but due to its low strength and poor corrosion resistance makes the development of magnesium alloy is limited.Aluminum as the same light structure material,especially aluminum alloy has good corrosion resistance.If the combination of the two can not only play the material phase complementary effect,and Al/Mg impedance discontinuity interface is expected to achieve better electromagnetic shielding performance.In this paper,Al/Mg/Al laminated composite plates are prepared by rolling composite.Considering that each component plate and its volume fraction will have some influence on the performance of the whole Al/Mg/Al laminated composite plates,three kinds of Al/Mg/Al laminated composite plates with different thickness ratios are designed,and the microstructure evolution law is studied using XRD,OM,SEM-EDS and other tissue analysis.The first nature principle was used to calculate and analyze the Al/Mg intermetallic compounds generated during the rolling process.The mechanical properties and corrosion properties were investigated by tensile testing machine and electrochemical workstation.The electromagnetic shielding properties of Al/Mg/Al laminated composite plates were also tested by micro-coaxial.The results of the study are as follows:（1）The characterization of the Mg-8Li-2Y-Zn alloy after homogenization annealing treatment yielded that the Mg-8Li-2Y-Zn alloy contains mainly three phases,α-Mg phase,β-Li phase and Mg₁₂YZn phase.After rolling deformation,theα-Mg grains andβ-Li grains in the Mg-8Li-2Y-Zn alloy are stretched and rolled long along the RD direction,and sharply rolled flat and refined along the ND direction,and theα-Mg grains andβ-Li grains are evenly arranged alternately.the Mg₁₂YZn phase is deformed from the initial large grains to small grains in the form of dots and bars.（2）The XRD pattern analysis of the exfoliated interfaces of Al/Mg/Al laminates with different thickness ratios shows that Al₁₂Mg₁₇,Al₃Mg₂ and other phases are mainly produced at the interfaces of the Al/Mg/Al laminates,which indicates that the prepared laminates have good interfacial bonding.The SEM-EDS also found that there was mutual diffusion of Mg and Al elements at the bonding interface of the Al/Mg/Al laminate,and it is presumed that the bonding mechanism of the Al/Mg/Al laminate prepared by asynchronous rolling is a diffusion mechanism.Meanwhile,the first nature principle calculates that Al₁₂Mg₁₇ is a brittle intermetallic compound and Al₃Mg₂ is a ductile intermetallic compound.Al₁₂Mg₁₇ has a more stable phase structure compared to Al₃Mg₂.（3）The Vickers microhardness of the Mg-8Li-2Y-Zn alloy master sheet after homogenization annealing treatment was 50.32 HV,and the hardness of the Mg layer of the laminated composite sheet increased after the rolling compound.The brittle phase was generated at the interface side between the Al and Mg layers,and the microhardness values were slightly higher than those on both sides;the tensile strength of the Al/Mg/Al laminated composite sheet increased significantly,reaching a maximum of 239 MPa when the thickness ratio was 1:6:1,which was 73%higher than that of the homogenized annealed Mg-8Li-2Y-Zn alloy.（4）Comparison of polarization curves reveals that the corrosion potentials of Mg-8Li-2Y-Zn alloy and Al/Mg/Al composite plate do not differ significantly,and the surface of the alloy does not change significantly during cathodic polarization,maintaining the original metallic luster,and when entering the anodic region,the current densities of the anodic branch and cathodic branch of Al/Mg/Al laminated composite plate are smaller than those of Mg-8Li-2Y-Zn alloy,then the Al/Mg/Al laminate is more corrosion resistant than the Mg-8Li-2Y-Zn alloy.（5）The electromagnetic shielding performance of Al/Mg/Al laminated composite plates with different thickness ratios showed the same trend with frequency:the electromagnetic shielding effectiveness decreased with increasing frequency,between 30MHz and 6000 MHz,and overall,the Al/Mg/Al laminated composite plates with a thickness ratio of 1:3:1 performed well.The initial electromagnetic shielding effectiveness of Mg-8Li-2Y-Zn alloy ranged from 61.49 d B to 106.56 d B.59.18 d B to116.28 d B for Al/Mg/Al laminates with 1:18:1 thickness ratio,61.81 d B to 114.69 d B for Al/Mg/Al laminates with 1:6:1 thickness ratio,1:3:1 Al/Mg/Al laminates with 1:6:1thickness ratio,and 59.18 d B to 116.28 d B for Al/Mg/Al laminates with 1:18:1 thickness ratio.All of them are excellent or good shielding materials.