Research On The Wettability And Brazing Behaviors Of SnAgCu-xTi On SiC

Silicon carbide(Si C)ceramic has been widely used in electrical and electric industries due to its high chemical stability,high corrosion resistance and low thermal expansion coefficient.In view of the disadvantages of high brittleness and difficulty in processing,active brazing has been used in the connection of silicon carbide ceramics or metals to form composite components with complex shapes or excellent properties of both ceramics and metals.Wettability test is an important part in predicting brazing properties of brazed joint ceramics.In present study,the wetting behavior of Sn0.3Ag0.7Cu(SAC)filler with various Ti content on Si C ceramic was investigated.The effect of temperature and Ti content on the wetting behavior and interfacial microstructure of SAC-Ti on Si C were discussed.The interfacial thermodynamics and spreading kinetics of filler,active mechanism of Ti were conducted.Finally,Si C/Si C were directly brazed using SAC-Ti fillers.The effects of Ti content and brazing temperature on microstructure and shear strength of brazed joints were also investigated.The effect of temperature and active element Ti content wetting behavior of SACx Ti filler on Si C ceramic was investigated using sessile drop method.With the increase of temperature Ti dissolution into the filler and accumulates on the surface of the silicon carbide.Then,the interface forms reactants,cause the contact angle linear decreased and finally reached the equilibrium stage.The results of isothermal wetting test with different Ti contents show that with the increase of Ti content,the equilibrium contact angle decreased first and then increases,and the shape of the equilibrium fillers changed from spherical to near spherical shape then changed into conical shape.When the Ti content reached 1.5wt.%,the minimum contact angle(9.3°)was obtained with the best wettability.When Ti content continues increase,Ti-Sn reaction speed increased,consumed a large amount of Ti element,resulting poor wettability.Ti element directly reacted with Si C generated Ti C and Ti5Si3,which improves the wettability of the filler and decreased contact angle.The wetting and spreading of the solder on the Si C surface was controlled by the chemical reaction at the interface.The higher the temperature,the faster the spreading.The apparent activation energy of SAC-Ti wetted on the Si C surface was 129.3 k J/mol.The Si C ceramics were brazed by SAC-Ti filler with different Ti contents.The effects of Ti content and brazing temperature on the microstructure and mechanical properties of the joints were investigated.The typical interfacial microstructure of the brazed joint is Si C/Ti C/Ti5Si3/?-Sn(Cu6Sn5+Ti6Sn5)/Ti5Si3/Ti C/Si C.Under the condition of 950°C for 10 min,the filling property of filler was well when Ti content was larger than 0.5wt%.With the Ti content increases,the filling performance of the filler turn better,and the brazing angle increases first and then decreases.The shear strength increases first and then decreases with the increase of Ti content.The highest shear strength of 35.7MPa was obtained with SAC-1.5wt.%Ti.Then the joint strength decreases due to the influence of Ti6Sn5.The fracture in the brazing joint along with brazing seam.With the increase of brazing temperature,the fillet height increases,the filling performance turn better.When the temperature increases,the interface reaction layer becomes thicker.When brazing temperature was lower than 950°C,the shearing strength increases with the increase of temperature,the joint breaks in the brazing seam,belongs to ductile fracture.After the temperature reached to 1000°C,the joint breaks transferred to the Si C ceramic matrix,and the fracture type belongs to brittle fracture.