The diffusion bonding of hydrogenated TC4 alloy and the mechanic property test are carried out. The diffusion hole close-up ratio and fracture are investigated by means of optical metallographic microscope and scanning electron microscope. The results show that the hydrogen is benefi cial to increasing the holes close-up ratio of TC4 diffusion bonding. With the diffusion bonding parameters increasing the diffusion holes decrease gradually. When bonded at 775℃ for 60min under a pressure of 4MPa

the diffusion holes disappear and the tensile strength of the joint is up to 1017MPa

which reaches 96% that of the base metal

and the fracture face exhibits tearridge and dimple pattern.