| Due to its excellent physical and chemical properties,aluminum Alloy is widely used in transportation,aerospace and other industries.The titanium alloy has the anvantages of lightweight,high strength,good fracture toughness,high heat resistance and good corrosion resistance,which is widely used in aerospace,auto and other fields.In order to achieve the goal of weight reduction,performance improvement and low cost,it has become an important direction that different materials are assembled together.Considering the characteristics of titanium alloy and aluminum alloy,they are assembled together.At present,some key problems exist in the welding of titanium and aluminum.Different kinds of compounds formed in large quantities.The high temperature of welding process is harmful to of aluminum.At the same time,many welding methods are difficult to realize the joining of complex and precise structure.This paper put forward a new method,which was ultrasonic assisted induction soldering.Firstly,the surface of the titanium was hot-dip aluminized,which could avoid the oxidation in the soldering process,improve wettability of filler and reduce the effect of high temperature on the aluminum alloy.The method has good applicability,low cost,high efficiency,which can meet the effective joining of the sealing structure,ring inlay structure and frame structure etc.In this paper,the hot dipping process and the soldering process were controlled and adjusted reasonably to obtain the reliable joints.The fracture didn't occur at the interface.The formation mechanism and the growth law of the interface reaction layer were analyzed.Surface macro morphology,cross section morphology and interface changes were studied for hot-dip coating on titanium alloy.The formation of smooth surface and a good interface between the coating and titanium could be obtained at 800?,but the long time would form a number of interfacial compound.The interfacial compound layer elements and the morphological structure were different.Two kinds of fillers of ZnAlCuAg and ZnAlCuSn were prepared and tested for their composition and properties.The wettability test of the two fillers was carried out.When the ultrasonic wave was applied for 1s,the two kinds of fillers could spread out on the surface of the coating.It was found that the wettability of the ZnAlCuSn was better than the ZnAlCuAg.Induction soldering of TC4 and 3A21 was carried out with the assisted ultrasonic wave.Soldering seam consists of the Zn element interface diffusion zone in the aluminum base metal,Al dissolution zone,the middle area of the seam and the metal compound layer.The highest joining strength was obtained by using Al-1.5Si.The fracture occurred on the base metal of aluminum alloy with a large number of dimples.In other cases,fracture occured at the interface.When the ZnAlCuSn was used,the fracture occured in the rich Sn phase due to the lower strength of Sn.The shear strength was not high.The formation and growth of interfacial reaction layer was analyzed.TiAl3,Ti(Al,Si)3,?1(Ti7Al5Si12)and Al20Ti2 Re were generated in the experiments.The reaction mechanism of different compounds was analyzed.When using pure Al,the interfacial compounds was the TiAl3 compound.When the coating contained of Si,Ti Al3,Ti(Al,Si)3 and ?1(Ti7Al5Si12)were generated.Al was completely dissolved after soldering.The filler and the compound layer were embedded in together.When using the Re element,compound on the interface remained TiAl3 and Al20Ti2 Re.Only the TiAl3 layer remains on the interface after soldering,while the Al20Ti2 Re moved into the soldering seam.Finally,the interface compound growth model of the hot dip coating process and soldering process were established. |
PDF Full Text Request