| Based on the needs of energy saving,resource saving and light weight,Cu/Al tubes are widely used in various fields of industry like refrigeration.It is a hot and difficult point to explore an efficient and reliable connection technology between Cu/Al tubes.Combining the advantages of magnetic pulse forming,semisolid forming and brazing,this paper proposes a new magnetic pulse-semisolid hybrid assisted soldering of Cu/Al tubes,which uses magnetic pulse force to drive the outer tube to high-speed extrusion of semisolid solder.The solid phase particles in the semisolid solder remove the oxide film on the surface of the base metal by radial compression and axial shearing on the surface of the base metal,and realize the fluxless brazing joint of Cu/Al tubes.In this paper,the magnetic pulse-semisolid hybrid assisted soldering of Cu/Al tubes was studied by numerical simulation and experimental analysis.Multi-physics coupling analysis of Cu/Al tubes magnetic pulse-semisolid hybrid assisted soldering was carried out by LS-DYNA software.The rheological behavior of semisolid Zn-Al solder and the interface force of outer tube were investigated.According to the results of finite element analysis,the magnetic pulse-semisolid hybrid assisted soldering test was designed,and the influence of semisolid Zn-Al solder composition and solid phase rate on welding quality was investigated.In the magnetic pulse forming,the flow speed of semisolid solder near the outside of the tube is largest;the inner semisolid solder flows inward,filling the gap between the outer tube and the inner tube,the flow rate is small;while the semisolid solder in the middle portion has almost no flow.The pressure amplitude of the outer tube decreases with the increase of the apparent viscosity of the semisolid solder,and the shear stress is increased as the apparent viscosity of the semisolid solder increases.The pressure amplitude and shear stress are substantially constant when the apparent viscosity is greater than 40 Pa·s.In the magnetic pulse-semisolid hybrid assisted soldering,the fluxless brazing joint of Cu/Al tubes can be realized when the solid phase ratio of the semisolid solder is 0.6.The joint weld zone is mainly composed of Zn-Al eutectic matrix and coarse?-Al,CuZn5 and ternary phase Al4.2Cu3.2Zn0.7;The zone near Al interface is mainly composed of?-Al and CuZn5,but the Al4.2Cu3.2Zn0.7 ternary phase is formed in Cu/Zn-22Al/Al joint.The microstructure of Cu interface is similar,which contains a thin diffusion layer close to the Cu interface and Al4.2Cu3.2Zn0.7 ternary phase.Compared with Zn-3Al and Zn-22Al,Zn-15Al is the suitable solder for the magnetic pulse-semisolid hybrid assisted soldering of Cu/Al tubes,because it has a suitable solid-liquid interval,and the Cu/Zn-15Al/Al joint has a better microstructure. |
PDF Full Text Request