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<p>The diffusion brazing of Ti2AlNb and Ti6Al4V (TC4) alloys using a TiZrCuNi filler alloy offers an effective method for producing high-performance joints in aerospace applications. This study investigates the evolution of the joint’s microstructure and mechanical properties under different brazing conditions, aiming to optimize the process for these dissimilar materials. The results show that under the optimal brazing conditions of 950&#xa0;°C for 60&#xa0;min at 5&#xa0;MPa, the joint achieves a peak tensile strength of 748&#xa0;MPa, about 88% of the strength of the matrix. The microstructure of the joint evolves from a brittle, eutectic (Ti,Zr)<sub>2</sub>(Cu,Ni) phase at lower temperatures to a more stable and homogeneously dispersed phase at higher temperatures. Initially, the intermetallic phase forms in a lamellar structure, which transitions into a networked form as the brazing temperature increases, ultimately resulting in a fine dispersion at the optimal brazing parameters. This transformation significantly improves the joint’s ductility and strength. The enhancement in mechanical performance is mainly attributed to the reduction of brittle phases at the interface, which mitigates stress concentration and prevents crack initiation. The fracture analysis reveals a shift in failure mode from brittle intergranular cracking to ductile microvoid coalescence. The finite element simulations further support this observation, showing that the suppression of brittle phases alleviates localized stress intensification, thus improving the joint’s fracture resistance. These mechanistic insights provide a theoretical and engineering basis for developing high-reliability titanium alloy hybrid joints.</p>

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Microstructure evolution and fracture mechanism of Ti6Al4V/Ti2AlNb vacuum diffusion brazing joints: interfacial regulation via TiZrCuNi interlayer

  • 期刊论文

  • 发表日期：

    2025年10月15日

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  • Yisheng Mou,
  • Yong He,
  • Han Zhao,
  • Yurong Liu,
  • Shangyu Yang,
  • Lihong Han

摘要

The diffusion brazing of Ti2AlNb and Ti6Al4V (TC4) alloys using a TiZrCuNi filler alloy offers an effective method for producing high-performance joints in aerospace applications. This study investigates the evolution of the joint’s microstructure and mechanical properties under different brazing conditions, aiming to optimize the process for these dissimilar materials. The results show that under the optimal brazing conditions of 950 °C for 60 min at 5 MPa, the joint achieves a peak tensile strength of 748 MPa, about 88% of the strength of the matrix. The microstructure of the joint evolves from a brittle, eutectic (Ti,Zr)2(Cu,Ni) phase at lower temperatures to a more stable and homogeneously dispersed phase at higher temperatures. Initially, the intermetallic phase forms in a lamellar structure, which transitions into a networked form as the brazing temperature increases, ultimately resulting in a fine dispersion at the optimal brazing parameters. This transformation significantly improves the joint’s ductility and strength. The enhancement in mechanical performance is mainly attributed to the reduction of brittle phases at the interface, which mitigates stress concentration and prevents crack initiation. The fracture analysis reveals a shift in failure mode from brittle intergranular cracking to ductile microvoid coalescence. The finite element simulations further support this observation, showing that the suppression of brittle phases alleviates localized stress intensification, thus improving the joint’s fracture resistance. These mechanistic insights provide a theoretical and engineering basis for developing high-reliability titanium alloy hybrid joints.