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Direct diffusion bonding of an orthorhombic Ti 2 AlNb base alloy to a TiAl base alloy, Ti-22Al-23Nb-2Ta and Ti-46.2Al-2Cr-2Nb-0.15B (at. pct), was carried out and the interface microstructure, formation of new phase at the interface and joint strength were characterized. At low temperature, a new phase with AlNb 2-structure, Al(Nb, Ti) 2 , was formed in the interface region adjacent to the O base alloy. The α 2 was found to be the major reaction product and developed in the interface region adjacent to the TiAl alloy as well as in the region adjacent to the O base alloy accompanying the formation of Al(Nb, Ti) 2 . The occurrence of Al(Nb, Ti) 2 has been attributed to the different diffusivity of Nb and Al, leading to a eutectoid-like reaction. At relatively high temperature, Al(Nb, Ti) 2 did not form due to enhanced diffusion of Nb but a B2-enriched zone formed on the O alloy side instead after long holding time. Only when an appropriate interface microstructure was achieved by optimizing the bonding parameters, could the shear strength of the joint reach 80% of that of the TiAl base alloy.
Direct diffusion bonding of an orthorhombic Ti 2 AlNb base alloy to a TiAl base alloy, Ti-22Al-23Nb-2Ta and Ti-46.2Al-2Cr-2Nb-0.15B (at. Pct), was carried out and the interface microstructure, formation of new phase at the interface and joint strength were characterized. At low temperature, a new phase with AlNb 2-structure, Al (Nb, Ti) 2, was formed in the interface region adjacent to the O base alloy. was found to be the major reaction product and developed in the interface region adjacent to the TiAl alloy as well as in the region adjacent to the O base alloy accompanying the formation of Al (Nb, Ti) 2. Ti) 2 has been attributed to the different diffusivity of Nb and Al, leading to a eutectoid-like reaction. At relatively high temperature, Al (Nb, Ti) 2 did not form due to enhanced diffusion of Nb but a B2-enriched zone formed on the O alloy side instead after long holding time. Only when an appropriate interface microstructure was achieved by optimi zing the bonding parameters, could the shear strength of the joint reach 80% of that of the TiAl base alloy.