Research On Integral Connection Technology Of Aluminum Alloy Multilevel Structure

At present,aluminum alloy thin wall and complex multilevel structure is widely used in radar antennas and radiators.The problem of the welding quality is not stable,the yield is not high appeared in Aluminum Alloy multilevel structure,because of its characteristics of complex shape,thin wall.narrow channel welding size,high requirements of the form and position accuracy and difficulty of manufacture.The method of brazing,brazing-diffusion welding and diffusion welding were applied to connect the composite multilevel structure of aluminum alloy.The influence of different parameters on joint interface,mechanical properties and deformation were analyzed by researching on the interf ace structure of welding joints.The ANSYS finite element analysis software was used to effectively control the welding deformation of parts and finally obtained ideal welding joints.The welding experiment was applied to weld the 3A21 aluminum alloy multilevel structure by using Al-Si-Mg solder.The best joints were obtained under the conditions of brazing temperature of 610 degrees centigrade and 10min preservation time,the best strength is up to 72MPa.The brazing-diffusion welding experiment was applied to weld the 3A21 aluminum alloy multilevel structure by using Al-Si-Mg solder.The ideal joints were obtained under the conditions of 610 degrees centigrade.10 min preservation time,diffusion welding temperature of 560 degrees centigrade,pressure of 0.5 MPa.60 min diffusion time,the strength of the joints can reach 81 MPa.The quality of the joints obtained by brazing-diffusion welding were better than the brazed joints.which is due to the elimination of the defects including without welding and cavities by diffusion welding after brazing.The EDS was used to analyze the welded joints of 3A21 aluminum alloy multilevel complex of structure,The elements in the base metal and solder were evenly diffused by both methods.and The diffusion of elements in the joints of brazing-diffusion welding is more even.The joints mainly includes the Al cellular matrixblock Si rich phase and primary Si etc.In addition.Mg2Si strengthening phase in the joints was formed by Mg and Si,so that the performance of the joints was improved.Direct diffusion welding was used to weld the multilevel structure of 6061 aluminum alloy.The optimal joints were obtained under the conditions of 560 degrees centigrade welding temperature.4MPa welding pressure,60 min the holding time.The highest strength can react to 143MPa.Adding Al-Si interlayer dilffusion welding was used to、weld the multilevel structure of 6061 aluminum alloy.The optimal joints were obtained under the conditions of 580 degrees centigrade welding temperature,30min welding time,2MPa welding pressure,520 degrees centigrade welding temperature for 60min,under 1MPa pressure.The strength can reach to 150 MPa.The EDS was used to analyze the welded joints of 6061 aluminum alloy multilevel complex of structure,The joints mainly includes the A1 cellular matrix,Al-Si eutectic,Si rich phase Mg2Si and etc.By using the method of sectional pressurization,the deformation rate can be reduced significantly,and the deformation rate is 0.3%percent smaller than that of the deformation rate of only one section.The design and optimization of welding method and process parameters was optimized under the guidance of the finite element simulation results,which effectively controlled the welding deformation of the parts.