Hot deformation study and interface characterization for TiAl/Ti₂AlNb diffusion bonds based on the serial constitutive model

In this work, the compressive deformation behavior and the microstructure evolution of bonding interface of TiAl/Ti₂AlNb dual-alloy joint were investigated comprehensively. An Arrhenius-type serial constitutive model was developed to describe the hot deformation behavior of TiAl/Ti₂AlNb joint. Based on the microstructure characterizations and composition analysis, it is found that small particles of Ti₃Al₂Nb intermetallics precipitated at the bonding interface adjacent to the Ti₂AlNb base material after hot compression. During hot compressing at 900 °C, the dominant deformation mechanism is demonstrated to be a dislocation-mediated creep accompanied by the decomposition and the reprecipitation of O phase in Ti₂AlNb. Moreover, O phase decomposition occurs in Ti₂AlNb when deforming at 1000 °C. The (α₂ + Ti₃Al₂Nb) grains layer and the α₂ phase transformation were captured at bonding interface. At the temperature of 950 °C and 1000 °C, it is revealed that the strain rate sensitivity parameter (m) tends to be 0.2 with the increase of deformation even though deforming at the strain rates of 0.1s⁻¹, 0.01s⁻¹, and 0.001s⁻¹, indicating a similar mechanism at large strain conditions under those various conditions. This work provides a strategy not only contributing to control the structure of bonding interface but also improving the processability of TiAl/Ti₂AlNb joints.