Microstructure Evolution Mechanism And Properity Of Brazed Joints Of Ti₅Si₃/TiAl And?Ti₅Si₃/TiAl?/Inconel 718 With The Ti-Zr-Cu-Ni Filler Alloy

In recent decades,with the development of science and technology the demand for new materials is growing,TiAl alloy because of its high specific strength,low density and other advantages in the field of aerospace show unprecedented application potential,however,its plasticity is poor,difficult to deformation and other issues also limits its development.Conventional Ni-based alloys have excellent strength,plasticity and oxidation resistance,but their density is too large and the phase performance has reached the limit.TiAl alloy and Ni-based alloy advantages complement each other,the two components can be connected to a special component which can play both advantages.As a result,there is a demand for the connection of TiAl alloy to Ni-based alloy.In this paper,Ti-Zr-Cu-Ni amorphous brazing filler metal was successfully used to braze the layered Ti₅Si₃/TiAl itself and the layered Ti₅Si₃/TiAl and Inconel 718,the influence of the change of brazing parameters on weld structure and joint performance was studied,and explained the formation of weld organization.Ti-Zr-Cu-Ni amorphous brazing filler metal was used to braze Ti₅Si₃/TiAl and a good combined,high strength joint was obtained.The typical microstructure was ?-Ti and the eutectoid structure ?-Ti+?Ti,Zr?2?Cu,Ni?in the weld,while the diffusion reaction zone consisted of Ti2Al/Ti3 Al and?Ti,Zr?2?Cu,Ni?.The maximum room temperature shear strength of 252 MPa was obtained when the joints brazed with 180 ?m Ti-Zr-Cu-Ni filler metal at 910? for 5 min.The diffusion of Al has an important effect on the morphology of the joint,the Al element diffuses into the weld through polyatomic synergism,while the diffusion reaction zone consisted of Ti2Al/Ti3 Al and?Ti,Zr?2?Cu,Ni?,the transition of ?-Ti??-Ti+?Ti,Zr?2?Cu,Ni?occurs at the location of the Al element in the center region of the weld,forming a striped eutectoid.At 650?,the strength of the joint increased to 434 MPa due to the anomalous phenomenon of the intermetallic compound.Ti₅Si₃/TiAl and Inconel 718 were also connected by Ti-Zr-Cu-Ni amorphous solder in the same manner as brazing,the typical microstructure was ?-Ti and the eutectoid structure ?-Ti+?Ti,Zr?2?Cu,Ni?in the weld.The reaction layer at the junction of Ti₅Si₃/TiAl and the brazing filler metal is the whisker structure composed of Ti2Al/Ti3 Al and?Ti,Zr?2?Cu,Ni?;while a dendritic NiCrFe crystal formed between Inconel 718 and the solder layer,adhesive layer of Ti-Ni,Ti-Cr,Ti-Fe intermetallic compound and Cr,Fe,Ti,Zr,Cu,Ni attached to each other.The maximum room temperature shear strength of 225 MPa was obtained when the joints brazed with 180 ?m Ti-Zr-Cu-Ni filler metal at 910? for 5 min.Under the condition that the brazing temperature is high and the holding time is long,the diffusion of Ni element is more complete,and the effect of the composition on ?-Ti+?Ti,Zr?2?Cu,Ni?eutectoid in the weld is gradually reduced,?Ti,Zr?2?Cu,Ni?phase of the solution-free Ti?s?is relatively increased,the thickness of the reaction layer between the Inconel 718 and the solder layer is slightly increased.At 650?,the joint shear strength increased to 382 MPa.