Research On Extrusion Connection Process Of Mg/Al Alloys Thickness-oriented Bonding Sheet

Solid phase bonding of magnesium/aluminum（Mg/Al）alloys has always been a research hotspot in lightweight forming.Although the traditional welding connection method plays a leading role in the modern Mg/Al bonding technology,the defects such as easy oxidation of Mg/Al alloys,substantial factor of linear expansion and generation of lots of Mg-Al intermetallic compounds will lead to the increase of welding difficulty,which limits the application of Mg/Al alloys bonding components in industry.Pressure bonding can avoid these problems and realize effective solid-phase bonding while plastic deformation of magnesium and aluminum metals.At present,Mg/Al alloys bonding components have been compounded in radial and normal directions.However,the interface contact area of magnesium and aluminum in the thickness direction is small and th e bonding process is difficult,which needs to be solved urgently.Therefore,this paper presents an extrusion process to realize stable connection in the thickness direction-the method of Mg/Al alloys thickness-oriented bonding sheet via hot extrusion.This method solves the sensitivity of Mg/Al alloys to welding method,and the introduced interface increases the friction and normal stress between magnesium/aluminum,the resulting shear deformation behavior promotes the interface bonding and grain refinement,and achieves the effect of forming-to-bonding in a single pass;the forming temperature has an important effect on the matrix structure and interface structure.It would obviously refine the grains of magnesium matrix structure.The recrystallization mechanism is composed of continuous dynamic recrystallization and discontinuous dynamic recrystallization.It would also make the aluminum matrix structure elongate into fibrous structure,and the softening mechanism would change from dynamic recovery to dynamic recrystallization;with the increase of temperature,the composition of the interface transition layer changes from Mg/Al solid solution to Mg/Al intermetallic compounds,and the bonding strengthen is best at 390°C,about 42 MPa;the annealing process is also important for the subsequent research of this process.The research shows that the influence of annealing temperature on the interface structure of Mg/Al alloys thickness-oriented sheets is greater than that of annealing time.After annealing,the interface transition layer changes from single-layer structure to double-layer structure composed ofγ-Al₁₂Mg₁₇ andβ-Al₃Mg₂ sublayers,the interfacial bonding strength of thickness-oriented sheets decreases with the increase of annealing time and annealing temperature;the intelligent algorithm is introduced to optimize and predict the interface bonding strength.The results show that the genetic neural network model has certain generalization ability.In conclusion,the method of Mg/Al alloys thickness-oriented bonding sheet via hot extrusion widens the existing thickness-oriented solid phase connection process and provides a new forming process means for lightweight development.However,the process is still under study,and its internal bonding mechanism and characterization methods need to be further studied.