| In recent years,in order to solve the problem of energy shortage and environmental pollution,the lightweight application mainly of aluminum alloy has a development prospect in the field of industrial technology.Welding is required in aluminum alloy applications.Superplastic bonding can avoid the problems of fusion welding.It has the advantages of diffusion welding and deformation welding,simple welding process,simple welding equipment.And compared with diffusion welding,the time is shorter,the temperature is lower.In this paper,Gleeble-3800 thermal simulation test machine is used to test the superplastic connection of 5083 aluminum alloy,and a new material connection method is explored,which provides a new idea for the future aluminum alloy connection.Aluminum 5083 is a typical Al-Mg alloy,which is widely used in automobile and rail transportation industries.In this paper,coarse-grained 5083 aluminum alloy was studied to study its high-temperature properties.The constitutive equation was obtained by using hyperbolic sine function Arrhenius equation to study the relationship between activation energy and temperature and strain rate.The deformation mechanism is analyzed by combining microstructure and activation energy.According to the results,the process parameters of superplastic bonding of coarse-grained 5083 aluminum alloy were developed.The effects of prestress,surface roughness,holding time and strain rate on the quality of superplastic connection were studied.High-temperature tensile tests were conducted on coarse-grained 5083 aluminum alloy at temperatures of 350℃～475℃and strain rates in the range of 1×10-4s-1～1×10-2s-1.The influence of each parameter on flow stress strain and elongation after fracture is analyzed.When the temperature is 400℃and the strain rate is 5×10-4s-1,the elongation of coarse-grained 5083 aluminum alloy is 149.5%.When the temperature is 450℃and the strain rate is 1×10-3s-1,the elongation after fracture is 139.5%.According to the true stress-strain curves under different deformation conditions,the strain rate sensitivity index“m”and deformation activation energy“Q”were calculated,and the m was between0.2934 and 0.3537.The constitutive equation of the hyperbolic sinusoidal function of the coarse-crystalline aluminum alloy 5083 was established,and Q=213.992k J/mol was calculated.The deformation mechanism was analyzed by combining the microstructure and activation energy,and the plastic deformation mechanism included grain boundary diffusion mechanism and dynamic recrystallization mechanism.The microstructure changes in the process of superplastic deformation were observed and analyzed by metallographic microscope,corresponding to the calculation results.The superplastic bonding of coarse-grained 5083 aluminum alloy was carried out by orthogonal test,and the effects of oxide film and interface roughness on joint quality was analyzed.It was found that when Sa≤0.17μm,the roughness has little effect on the joint,and a certain roughness can make the joint tighter.When the prestress is greater than20MPa,the joint will be greatly deformed.Therefore,selecting the prestress of 10 MPa can make the metal layer thinner and smaller while achieving a good connection.Through the analysis of tensile strength results,The optimum superplastic bonding parameters are connection temperature 450℃,prestress 10MPa,holding time 40min and strain rate1×10-3s-1,and the joint strength is 171MPa.There is no obvious connection defect in the structure and no fracture position at the interface.5083 aluminum alloy realizes reliable connection through superplasticity. |
PDF Full Text Request