Interface characteristic and mechanical performance of TiAl/Ti ₂ AlNb diffusion bonding joint with pure Ti interlayer

Abstract

Abstract Solid‐state diffusion bonding (DB) of TiAl alloy and Ti 2 AlNb alloy was carried out using pure Ti as an interlayer at 1000 °C under 20 MPa for 60–120 min. The effects of bonding times on the interfacial microstructure and mechanical performance of the TiAl/Ti/Ti 2 AlNb bonded joints at room temperature (RT) were investigated detailly. The results demonstrated that the diffusion layers (DLs) mainly consisted of four characteristic layers, (I) single coarse α 2 phase adjacent TiAl alloy, (II) single refined α 2 phase at the bonding interface, (III) equiaxed/acicular α 2 phase embedded in β phase adjacent Ti 2 AlNb alloy and (IV) both equiaxed α 2 phase and acicular O phase embedded in β phase adjacent Ti 2 AlNb alloy, respectively. The thickness of the four layers increased with the increasing of the bonding time. The growth of DLs is controlled by diffusion and the reaction rate constant k for region I, II, III and IV are 1.22 × 10 −6 , 1.27 × 10 −6 , 2.6 × 10 −7 and 7.7 × 10 −7 m·s −1/2 , respectively. Meanwhile, the interface α 2 grain grows up without texture. The maximum tensile strength of 281 MPa was maintained at 1000 °C for 90 min under the pressure of 20 MPa. Consequently, the phase transformation and dynamic recrystallization behavior of the DLs were discussed.