Microstructure and properties of pulse current promoted diffusion welding TiAl/Ti2AlNb joint with Ti69NbCrZrX interlayer

The novel Ti69NbCrZrX （X=Sn，W，Al，Mo，1%-2%， mass fraction） was used as an interlayer to join TiAl alloy with Ti2AlNb alloy by pulsed current diffusion welding at 900 ℃/30 min/8 MPa. The post-weld joint microstructure and properties were analyzed by SEM， EDS， EBSD， and room temperature tensile test. The results show that defect-free TiAl/Ti2AlNb joints can be obtained using Ti69NbCrZrX as the connecting interlayer. The joint interface microstructure is mainly composed of TiAl diffusion affected zone， interlayer diffusion zone， and Ti2AlNb diffusion affected zone. The TiAl diffusion affected zone structure is composed of white β phase and gray block α2 phase，the interlayer diffusion zone structure is mainly composed of gray block α2+ α phase， and white β/B2 phase composition， Ti2AlNb diffusion affected zone is composed of β/B2 matrix phase with lath and acicular O phase. The average value of room temperature tensile strength of the joint is 642.5 MPa， which reaches 91.57% of the strength of the base material. The fracture mode of the joints is dominated by brittle intergranular fracture， supplemented by brittle transgranular fracture.