Effect of beam offset on the microstructure and mechanical properties of electron beam welded joints between Ta and GH4169 alloy

This study investigated the effects of different beam offset distances on the microstructure and mechanical properties of Ta/GH4169 welded joints. The results showed that all joints fractured at the fusion line on the Ta side. The strength of the joint first increased and then decreased with the increase of the offset distance to the Ta side. When the beam offset distance was 0.5 mm, the strength of the joint was the highest, reaching 348 MPa at room temperature and 298 MPa at 400 °C, which were 268% and 481% higher than those of the joint without beam offset. The microstructure analysis indicated that the weld was mainly composed of FCC phase, FCC + Laves eutectic phase and BCC particles. Among them, the FCC phase formed a stable coherent interface between the Laves phases. In addition, a high density of nanoscale coherent L1₂ precipitates was uniformly distributed within the FCC matrix. These precipitates contributed to the strengthening of the FCC matrix and participated in local dislocation-mediated deformation, as evidenced by the formation of dislocation channels and deformation microbands. However, this beneficial effect was mainly confined to the microscopic scale within the weld metal. The overall tensile response of the joint was still predominantly governed by premature fracture near the brittle reaction layer on the Ta side. These results provide important references for the high-quality bonding of Ta with Ni-Fe-based materials, as well as for the development of high-strength eutectic high entropy alloys.