Combining fasting diffusion and microstructure regulation to achieve high-quality diffusion bonding of Ti2AlNb/TA2 at low temperature

In order to reduce the loss of the mechanical property of the Ti 2 AlNb-based alloy after the hot processing, lowering the temperature of the diffusion bonding is a competitive approach in the fabrication of multi-layer structural components. In this work, surface mechanical attrition treatment (SMAT) is applied to the Ti 2 AlNb-based alloy and the TA2 titanium for 6 h and 3 h to obtain the gradient nanostructure , respectively. Different states of TA2 titanium and Ti 2 AlNb-based alloy specimens are diffusion-bonded into the dissimilar alloy joints at a low temperature of 800 °C under the pressure of 10 MPa for 1 h. Along with the change in surface states , the microstructure, interface, phase transformation, and the corresponding mechanical properties are carefully analyzed. The orientation relationship of the phases in the reaction zone, the effect of gradient nanostructure (GNS) on the diffusion behavior , and the strengthening mechanisms of joints are discussed in detail. The joint, boned with SMAT-processed TA2 and Ti 2 AlNb alloys, present a shear strength of 506.1 MPa, 46.2 % higher than the joint bonded with the original state. The excellent mechanical of the joint is attributed to the broadening of the diffusion zone , the appropriate distribution of the generated phases in the reaction zone, and the more favorable morphology of reinforcements. The presented findings provide a new interface design strategy for obtaining the high-mechanical-performance joint of Ti 2 AlNb alloy at low temperatures. • Ti2AlNb/TA2 joint is well diffusion-bonded at a low temperature of 800 °C via the SMAT process. • The microstructure, phase transformation, interface, and mechanical properties are carefully investigated. • The influences of the gradient nanostructure on the diffusion-bonding process are meticulously dissected. • Fasting diffusion and microstructure regulation endow the joint with brilliant shear mechanical properties.