Technology And Mechanism Of Brazing C/SiC Composite And TC4 Titanium Alloy

C/Si C composite which has a low density, high temperature resistance, high strength and anti ablationa has been widely used in aerospace and other fields as a new material. Titanium alloy has a high strength, high toughness, high temperature resistance and other excellent. Brazing TC4 alloy and C/Si C composite can be used as nozzle member of rocket engine. It may reduce the structural weight, obtain better high temperature performance and improve the efficiency of rocket engine. However, there are some difficulties in the brazing of those two materials since their difference in coefficient of thermal expansion(CTE) and elastic modulus would produce great thermal residual stress. In this paper, Si C porous ceramic and hydrogenated TC4 alloy were used as intermediate layer for solder joint of hydrogen achieved TC4 alloy and C/Si C composite. Combining the experimental results and the theoretical calculations,the typical microstructure was analysised. The mechanical properties of the joints were investigated. The thermodynamics of interface product and the fracture behavior of joints were explained. And the microstructure evolution and the mechanisms of intermediate layer was revealed.TC4 alloy and C/Si C composite were brazed with a Si C porous ceramic was used to adjust CTE from the aspects of structure. The typical interfacial microstructure of the joint is: TC4 alloy/α-Ti+β-Ti/Tix Cuy/Cu(s.s)+Ag(s.s)/Tix Cuy/Ti5Si3+Ti C/Si C porous ceramic/Ti C+ Ti5Si3/Cu(s.s)+Ag(s.s)/Tix Cuy/Ti5Si3+Ti C/C/Si C composite. The highest shear strength at room temperature can be obtained when hating temperature is 860℃,holding time is 10 min, which is 89 MPa. The fracture always occurred inside the C/Si C composite.Hydrogenated TC4 alloy(hydrogen content was 0.3 wt%) was used as intermediate layer to make the microstructure uniform. The typical interfacial microstructure of the joint is: TC4 alloy/α-Ti+β-Ti/Tix Cuy/Cu(s.s)+Ag(s.s)/Tix Cuy/α-Ti+β-Ti/0.3wt%hydrogenated TC4 alloy/α-Ti+β-Ti/Tix Cuy/Cu(s.s)+Ag(s.s)/Tix Cuy/Ti5Si3+Ti C/C/Si C composite. Keeping holding time being10 min, when hating temperature are 860℃,880℃ and 900℃, the shear strength of the joints at room temperature can be 110 MPa,91MPa, 63 MPa, which were about two times as compared soldering without intermediate layer.When Si C porous ceramic + hydrogenated TC4 alloy( hydrogen content was0.3wt%) composite interlayer was used, the typical interfacial microstructure of the joint is: TC4 alloy/α-Ti+β-Ti /Tix Cuy /Cu(s.s) +Ag(s.s) /Tix Cuy/Ti5Si3+Ti C/Si C porousceramic/Ti C+Ti5Si3/Tix Cuy/Cu(s.s)+Ag(s.s)/Tix Cuy/α-Ti+β-Ti/ hydrogenated TC4alloy/α-Ti+β-Ti/Tix Cuy/Cu(s.s)+Ag(s.s)/Tix Cuy/Ti5Si3+Ti C/C/Si C composite. The highest shear strength at room temperature can be 121 MPa when hating temperature is860℃, holding time is 10 min. From the perspective of structure, Si C porous ceramic played a role in adjusting CTE. From the perspective of microstructures, hydrogenated TC4 alloy could make the microstructure uniform. As a result, the mechanical properties of the joint can be improved.