Diffusion Welding Of TC4 Titanium Alloy And LY12 Aluminum Alloy

Diffusion welding of titanium and aluminum dissimilar alloy has broad applications in the area of the national economy and national defense and military fields. It also can exert the good properties of two alloys synthetically. And ti is significant for reasonably, efficiently and fully using titanium alloy and aluminum alloy.In this paper, TC4 titanium and LY12 aluminum alloy were welded together by vacuum diffusion welding, and TC4/LY12 welded joints were obtained successfully. TC4/LY12 optimal welding process parameters were obtained by the tensile strength, ultrasonic measurement of welded specimens. And we also adopted XRD, SEM, EDS and microhardness tester to get the mechanism of element diffusion and the interface formation of intermetallic compounds.The process system of TC4/LY12 diffusion welding is as follows:When welding temperature is 570℃, holding time is 60 minutes, welding pressure is 10MPa, the tensile strength of joint reaches its maximum at 31.70MPa. The fracture of the tensile specimen shows that the fracture occurred in the Al matrix and the diffusion interface. There are some small holes on TC4 side fracture surface while many small granular material on LY12 side fracture surface.The microhardness, microstructure, the phase and EDS analysis of tensile fracture show that, the a-Ti solid solution and a small amount of TiAl₃ intermetallic compounds appear on the TC4 side fracture surface and the particulate matters on LY12 side are mainly TiAl₃ compounds and a small amount of Al(ss, Ti) solid solution, in addition, Mg element enrichment appears on the granular material. Therefore, the joint fracture is mainly due to the appearance of intermetallic compounds TiAl₃.Welded joints reaction layer products are decided by thermodynamics and kinetics factors. Growth models of reaction layers of TC4 titanium and LY12 aluminum alloy welding joints are divided into the following stages:effective physical contact,α-Ti and Al(ss, Ti) solid solution generating, TiAl₃ intermetallic reaction layer generating, and intermetallic layer growing.