Study On Vacuum Brazing Of TC4 Titanium Alloy And 304 Stainless Steel And The Microstructure And Properties Of Joints

Titanium alloy materials have become irreplaceable important strategic materials in the fields of military,aerospace and marine engineering due to their excellent properties such as good corrosion resistance,high fatigue strength,and high specific strength.However,the processing and molding process of titanium alloy materials is complicated and titanium alloy materials are expensive.In industrial manufacturing,titanium alloy materials are often not used alone,but they are always used with other materials to make composite structures to achieve complementary advantages.In this paper,a new type of TiZrCuNi amorphous filler and traditional AgCu eutectic filler are used to conduct vacuum brazing tests on TC4 titanium alloy and 304 stainless steel,and characterization methods such as XRD diffraction,SEM scanning electron microscope,EDS energy spectrum experiment and shear experiment will be used.The interfacial structure of the brazed joint,the diffusion of elements in the base metal and the brazing filler metal,the interfacial reaction during the welding process,the phase composition and the reaction mechanism are systematically studied.The results shows that the brazing joints prepared with TiZrCuNi amorphous filler,when the brazing temperature is T=980?,and the holding time t=10min,Ti-Fe intermetallic compounds and a small amount of(Ti,Zr)2(Ni,Cu)intermetallic compound are found in the joints.The wettability of TiZrCuNi amorphous filler to 304 stainless steel under different welding process parameters is relatively poor,and there is good compatibility between TiZrCuNi amorphous filler and TC4 titanium alloy.Increasing the brazing temperature is conducive to the dissolution of the 304 stainless steel base material into the brazing filler metal,but it will cause the increase of intermetallic compounds in the weld.The process parameters under the experimental conditions are brazing temperature T=980?,holding time t=10min,and obtaining the maximum shear strength of 154.3MPa.When brazing with AgCu eutectic filler,a large number of Ag-based solid solutions and some Ti-Cu intermetallic compounds and other reactive phases are observed in the joint interface.When the process parameters are brazing temperature T=820? and holding time t=10min,the interface microstructure of the brazing joint is:y-Fe+TiFe/Cu2Ti+TiFe/Ag-based solid solution/CuTi/?-Ti+a small amount of CuTi.With the increase of the brazing temperature or the extension of the holding time,the element diffusion between the brazing filler metal and the base metal is more sufficient,and the interface reaction of the joint is intensified,resulting in the increase of the brittle Cu-Ti intermetallic compound content in the weld.At the same time,it will also cause the loss of AgCu filler,and the content of Ag-based solid solution in the central area of the weld will decrease.When the brazing temperature T=820? and the holding time t=10min,the thickness of the interface reaction layer of the joint is moderate,the content of brittle intermetallic compounds is small,and the shear strength of the joint reaches 348.7MPa.