Study of Diffusion Bonding of Fine Grain TC21 Titanium Alloy

The diffusion bonding of TC21 titanium alloy with initial grain size of 2 mu m was performed at 780-980 degrees C for 5-90 min. The microstructure, bonding quality, microhardness and deformation ratio of the joints were analyzed. It is found that the interface bonding ratio can achieve 100% and the deformation ratio can be controlled within 10% when diffusion bonding is performed at 880 degrees C for 15-30 min. The microhardness of the joints increases with increasing of bonding temperature, but it shows a peak value as the bonding time is prolonged. When the joint is bonded at 880-930 degrees C, fully equiaxed structures are observed, and with increasing of bonding temperature, the sizes of alpha and beta phases are increased; but when bonding temperature is up to 980 degrees C, fully lamellar structures are obtained. When the joint is bonded at 880 degrees C for 5-60 min, the size of alpha and beta phases increases with prolonging of bonding time. However, when the bonding time is prolonged to 90 min, the sizes of alpha and beta phases decrease slightly.