Interface characteristic and mechanical performance of TiAl/Ti2AlNb diffusion bonding joint with pure Ti interlayer

Abstract

Solid-state diffusion bonding (DB) of TiAl alloy and Ti2AlNb 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/Ti2AlNb 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 α2 phase adjacent TiAl alloy, (II) single refined α2 phase at the bonding interface, (III) equiaxed/acicular α2 phase embedded in β phase adjacent Ti2AlNb alloy and (IV) both equiaxed α2 phase and acicular O phase embedded in β phase adjacent Ti2AlNb 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 α2 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.