Study On Microstructure And Properties Of TA2/S316 Diffusion Welding Joints

Titanium alloy has the advantages of high specific strength and strong corrosion resistance,and has a broad application prospect in the fields of aerospace,chemical production,etc.The welding structure of titanium alloy and stainless steel can make full use of the excellent properties of titanium alloy and reduce the cost,which has great significance to the popularization and application of titanium alloyIn this paper,diffusion welding method is used to prepare titanium/steel joint,and the influence of welding parameters on the structure and properties of the joint is studied.The method of adding intermediate layer is used to improve the joint performance,and the optimization mechanism is analyzed.The welding temperature and holding time have great influence on the structure and properties of the joint,especially the welding temperature.In the process of direct diffusion welding,when the temperature is between 910??970? and the holding time is 50?110 min,the joints with small deformation,uniform structure and good performance can be obtained.Among them,the joints with the best performance can be obtained at 940? and 80 min,and the shear strength is 110.47 MPa.Intermetallic compounds such as Fe2Ti?Cr2Ti and FeTi are formed near the interface.At the interface of TA2/S316,the phenomenon of Cr atom aggregation leads to the formation of a large number of Cr-Ti compounds,which increases the brittleness.It was found that the hardness of Cr atom aggregation region was the highest,reaching 475HV.When observing the fracture morphology and detecting the fracture phase,it is found that the fracture position of the joint is in this area,and the fracture distributes cleavage platform,which is brittle fracture.The main fracture phases include Fe2Ti,Cr2Ti,FeTi and Ti2FeNi.When Cu foil and Ni foil were added as the interlayer,the microstructure and properties of the joint changed.When Cu foil is used as the middle layer,Ti atoms can pass through the boundary of Cu foil to stainless steel.Intermetallic compounds such as FeTi?FeTi2?CuTi and Cu2Ti are formed near the interface.The addition of Cu foil does not inhibit the formation of brittle compounds,so the joint performance is not improved,and the maximum shear strength is 102.83 MPa.The fracture of the joint occurs on the Cu foil,mainly composed of CuTi,FeTi2 and other compounds.When Ni foil is used as the middle layer,Ni foil prevents the diffusion of Fe,Cr and Ti atoms.The phenomenon of Cr atom aggregation disappears and there is no brittle compound in the joint.The structure of the joint area is Ni based solid solution/TiNi/Ti2Ni?TiNi/?-?Ti.The joint performance is greatly improved.The maximum shear strength reaches 200.17 MPa,which is about 80%higher than that of direct diffusion welding.The fracture of the joint occurs on the Ni foil,and the fracture mainly consists of TiNi,Ni and other phases.