Research On Process And Mechanism Of Diffusion Bonding Tial Alloy To Ti₃AlC₂Ceramic

TiAl alloy is a kind of material with high specific strength, high specific stiffnessand high temperature property. Ti₃AlC₂ceramic which owns the properties of bothceramic and metal, is widely used in the field of aerospace. However, the report ofjoining of Ti₃AlC₂ceramic can be seldom found. The manufacturing of some keystructures of a new aerospace engine can be realized by joining of the two materials. Thispaper mainly realized the joining of Ti₃AlC₂ceramic and TiAl alloy with Zr/Ni、Ti/Nicomposite interlayer. The effects of joining parameters on the microstructure and theshear strength of the joint were discussed. The optimized joining parameter was achievedand the fracture of the joint was analyzed. The mechanism of diffusion was discussed.When Ti₃AlC₂ceramic and TiAl alloy were bonded directly, the typicalmicrostructure was TiAl/TiAl₂/TiAl₂+TiAl₃/Ti₃AlC₂+TiCx/Ti₃AlC₂. The highest strengthof53.1MPa was achieved when the bonding parameters was1000℃for60min.During the process of shear test, the fracture generated at the interface and thenpropagated into the ceramic. And finally the fracture took place at the interface. The jointcannot be achieved when the joining temperature was low, while the residual stress in thejoint would grow up resulting in cracks when the joining temperature was high.In order to relieve the residual stress, Zr/Ni interlayer was introduced in directdiffusion bonding of Ti₃AlC₂ceramic and TiAl alloy, and the typical interfacialmicrostructure of the joint was: TiAl/Al₃NiTi₂+TiAl/Al₃NiTi₂/AlNi₂Zr/AlNi₂Zr+Ni10Zr7/Ni7Zr2/Ni5Zr/Ni/Ni₃（Ti,Al）/Ni₃Al+TiCx+Ti₃AlC₂/Ti₃AlC₂. The fine bonding ofthe joint was achieved by the generation of the Zr（Ti）-Al-Ni eutectic. The bonding ofZr/Ni was weak when the joining temperature was low while Ni foil totally took part inthe reaction and reduced the residual stress when the joining temperature was high. Thehighest strength of75.2MPa was achieved when the bonding parameters was825℃for60min. The fracture took place at the interface of Ni/Ti₃AlC₂and inside the ceramic.Considering the intensive reaction and dissolution, Ti/Ni interlayer was introducedin direct diffusion bonding of Ti₃AlC₂ceramic and TiAl alloy, and the typical interfacialmicrostructure of the joint was TiAl/Al₃NiTi₂+Ti3Al/Ti3Al/Tiss+Ti₂Ni/Ti₂Ni/NiTi/Ni₃Ti/Ni/Ni₃（Ti,Al）/Ni₃Al+TiCx+Ti₃AlC₂/Ti₃AlC₂. Ni diffused through the grainboundary, resulting the decomposition of Ti₃AlC₂and the generation of TiCx. TheKirkendall holes decreased with the increase of the bonding temperature. As thetemperature continued growing up, Al₃NiTi₂and Ti₂Ni grew up and the residual stresswill increase and cracks can be observed at the interface. The highest strength of85.2MPa was achieved when the bonding parameters was850℃for60min under the pressure of30MPa. The fracture took place at the interface of Ni/Ti₃AlC₂and inside theceramic.