Rolling Method Of Al/Mg/Al Composite Plate And Mechanism Of Microstructure And Property

With the development of industry,lightweight materials have been paid more and more attention.Magnesium(Mg)alloys have been gradually applied to aerospace,automotive,chemical,3C and other fields due to their low density,high specific strength,good electromagnetic shielding and damping properties.However,the inherent close packed hexagonal structure of Mg alloy limits its plastic deformation ability,and more importantly,its non-corrosion resistance also restricts the industrial application of magnesium alloy.Aluminum(Al)alloy has excellent corrosion resistance,high specific strength and good processing performance.Therefore,Al alloy is used as the cladding plate of magnesium alloy,and the Al/Mg/Al sandwich structure is formed by rolling process.It not only improves the corrosion resistance of magnesium alloy,but also makes the composite plate have many advantages such as light weight,high strength,etc.For this reason,this paper proposed a rolling process to realize stable connection with the aid of hard plate rolling of Al/Mg/Al composite plate.The method combined large reduction with one-pass rolling forming,and solved the problems of long traditional rolling process and poor formability of sheet metal.Hard plate rolling improved the energy storage in deformed grains of Mg matrix plate,and the increase of dislocation density in coarse grains significantly improved the nucleation rate of recrystallization.The higher Schmid factor of base plane slip promoted the formation of recrystallization and realizes the refinement of the structure.The hard plate rolling could change the shear stress of rolled plate into compressive stress and change the metal flow mode of composite plate,so a special connection mode of differential flow was formed at the plate interface to produce corrugated interface.The corrugated interface could not only realize mechanical interlocking,but also promote the fresh metal to break through the oxide layer to increase the contact area,so that the metallurgical bonding was more sufficient.The corrugated interface introduced by the hard plate rolling had significantly strengthened the welding force between Al/Mg plates,and the maximum interface bonding strength could reach 64 MPa.Compared with the traditional rolling,the tensile strength and elongation of Al/Mg/Al composite plate rolled by hard plate under the same conditions were increased by about 30%,realizing the double increase effect of mechanical properties.Annealing was also important for composite sheets.After annealing treatment,it was found that the twins introduced into the rolled sheet induced static recrystallization during the annealing process.The shear band consisting of recrystallization gradually engulfed the deformed grains and further refined the structure.In addition,the formation and growth of the interlayer at the junction of heterogeneous plates were related to many factors.Therefore,by adjusting the annealing time and temperature,the diffusion layer between component layers could achieve the best effect,and finally achieve the goal of strengthening the interface bonding strength.