Microstructure And Properties Of Thin Plate Brazed Joint Between TiBw/TC4 And GH4169

Titanium matrix composites has the advantages of light weight,heat resistance,high strength and toughness,showing great potential in high temperature resistant structural parts,but it is not stable in the environment higher than 700 ?.Ni-base superalloy has the advantages of high strength and high heat resistance,but it has the disadvantages of high density and high cost.In order to further expand the application of titanium matrix composites to reduce the weight of high-temperature structural parts,and maximize the use of the advantages of titanium matrix composites and Ni-based superalloys,it is important to study the feasibility of welding titanium matrix composites and Ni-based superalloys and analyze the mechanism of joint formation.In this paper,a practical and efficient welding method based on TIG heat source is developed to realize the dissimilar connection between TiBw/TC4 composites and GH4169 alloy.The effects of welding method,welding process parameters and brazing filler material on the microstructure and mechanical properties of the joint are studied.The evolution of the microstructure of the joint and its relationship with the mechanical properties of the joint are revealed as well.The microstructure of the joint formed by Ti-Zr-Cu-Ni and Cu filler materials is analyzed,and the forming mechanism of the joint based on TIG heat source is explored.The microstructure and properties of the joint obtained by brazing in the furnace with Cu and other filler materials are analyzed,and the forming process of brazed joint obtained in furnace is discussed.It is found that the brazed joints of TiBw/TC4 composites and GH4169 alloy can be obtained by welding with TIG heat source,lap joint and arc on TiBw/TC4 composites,which provides a new and efficient welding method for joining of Titanium matrix composites and Ni-based alloy.The joints can be divided into melting and recrystallization zone of TiBw/TC4 composites,TiBw/TC4 composites,weld and GH4169 alloy.The products in the weld are brittle Ti-Ni intermetallic compounds.When the welding current and welding speed match well,the maximum joint shear strength is 56 MPa(70 A,90 mm/min).In order to reduce the formation of Ti-Ni brittle intermetallic compounds in the joint,amorphous Ti-Zr-Cu-Ni and Cu were selected as brazing filler materials for brazing using TIG heat source.Almost all of the products in the joints using Ti-Zr-Cu-Ni amorphous foil are(Ti,Zr)2(Cu,Ni).However,a Laves phase thin layer was formed at the interface between the weld and GH4169 alloy.While,as a filler material,Cu can effectively reduce or even inhibit the formation of Ti-Ni intermetallic compounds,and obtain excellent TiBw/TC4 composites and GH4169 alloy dissimilar joints.The products of the weld are closely related to the heat input.When heat input changes from low to high,the products in the weld change from Ti-Cu intermetallic compounds to Ti-Ni-Cu compounds and then to Ti-Ni-Cu compounds with a small amount of Ti-Ni intermetallic compounds.The shear strength increases first and then decreases with the increase of heat input(the increase of welding current or the decrease of welding speed).When the Cu filler material is 0.02 mm,there is more Cu in the weld which is not fully reacted and there is no Ti-Ni intermetallic compounds formed.When Cu is used to brazing TiBw/TC4 composite and GH4169 alloy using TIG heat source,Ti element and Cu element in the base metal diffuse each other to form a eutectic reaction to form a liquid phase,which interacts with the base metal on both sides.After cooling,the metallurgical combination of the base metal on both sides is realized.Under the condition of TIG heat source,the brazed joint strength is closely related to the welding parameters.The maximum shear strength of the joint obtained by amorphous Ti-Zr-Cu-Ni filler material is 200 MPa,and the corresponding welding process is 100 A and 100 mm/min.Different thickness Cu corresponds to different welding parameters.The highest shear strength of joints with Cu thickness of 0.04 mm is 208 MPa,corresponding to process parameters of 60 A and 90 mm/min.The highest shear strength of joints with Cu thickness of 0.1 mm is 370 MPa,corresponding to parameters of 100 A and 110 mm/min.The highest shear strength of joints with Cu thickness of 0.2 mm is 616 MPa,corresponding to process parameters of 90 A and 100 mm/min.Under furnace brazing conditions,both amorphous Ti-Zr-Cu-Ni and Cu can obtain excellent thin-walled TiBw/TC4 composite S and GH4169 alloy dissimilar joints.When amorphous Ti-Zr-Cu-Ni is used as filler material,the filler melts to form a liquid phase in the process of brazing heating,the element diffusion between the liquid phase and the base metal,and the eutectoid reaction occurs during cooling.The joint weld is formed by(Ti,Zr)2(Cu,Ni)and eutectoid structure of(?+(Ti,Zr)2(Cu,Ni)).The highest shear strength of the joint is 241 MPa at 900 ?/holding for 5 min.The Ti-Cu intermetallic compounds and eutectoid structure are the main products in the brazed joint using Cu filler material.The shear strength increases first and then decreases with the increase of holding time and brazing temperature.The maximum shear strength is 380 MPa,and the corresponding process parameter is 910 ?/holding for 5 min.