Effect of bonding temperature and holding time on properties of hollow structure diffusion bonded joints of TC4 alloy

The hollow structure commonly used in aerospace field is generally formed by the SPF/DB, but its disadvantages lead to surface groove and complex internal structure difficult to form. In this paper, the method of milling combined with diffusion bonding is used to improve the defect. Diffusion bonding of TC4 titanium alloy hollow structure was carried out at temperature ranging from 800 °C to 900 °C for 10 ~ 30 min. The interfacial bonding ratio, deformation ratio, microstructures, microhardness and mechanical properties of the diffusion bonded joints were investigated. The results show that joints with high bonding quality can be obtained when bonded at 850 °C and 900 °C for 20 ~ 30 min. The joint bonding ratio is more than 92%, the tensile strength is 952 MPa, and the deformation ratio is maintained at about 10%. The microhardness of the TC4 alloy hollow structural joint increases with the increase in bonding temperature, showing a trend of "high in the middle and low on both sides", and it has a peak value (HV472) when bonding time is prolonged up to 30 min. The findings indicate that qualified workpiece can be obtained by the process.