Research On Low-silver Brazing Filler Metal And Welding Mechanism For Alumina Ceramic Brazing

Because of its unique physical properties and internal organizational structure,ceramics have always attracted the attention of many scholars.The development of connection technology allows ceramic materials to be used in combination with traditional metal materials,and the two can make up for each other's shortcomings.The main research of this subject is a kind of low-silver solder brazing Al₂O₃ceramic and metal brazing process and welding mechanism.By preparing the solder powder,determine the DTA curve,wettability,and filling of the solder;perform ceramic-metal brazing connection according to the melting point characteristics of the solder to obtain the appropriate holding temperature and holding time;Shear and tensile failure tests summarize the reliability of solder in connecting ceramics and metals;analyze the welding seam with scanning electron microscope and energy spectrometer to summarize the welding mechanism of solder.Based on the analysis of the experimental results,the following conclusions are drawn:(1)Ag50Cu Sn Ni solder can be made by laboratory gas atomization,and the solder has a good particle size without obvious oxidation.The liquidus line of the solder can be measured as 784.2?by DTA analysis.(2)Using Ag50Cu Sn Ni and Ag72Cu respectively for ceramic-metal brazing,by changing the brazing temperature,the holding time,and the metal base material,the holding temperature is 810°C and the holding time is 8 minutes,and the manufactured brazing joints have high reliability.Through the shear tensile failure test,the test results show that the fracture positions of the brazed joints all occur on the ceramic side,indicating that the brazing filler metal can meet the requirements of ceramic-to-metal brazing.(3)The optical microscope observation of the weld seam at the brazed joint revealed that the brazing temperature would change the structure of the weld seam.Using scanning electron microscope observation and energy spectrum analysis of the weld seam,it is concluded that the weld seam area is mainly composed of three parts:The first is the continuous distribution of Ag,Sn,and Ni solid solutions with Cu as the matrix that are first precipitated at the interface bonding position.According to the analysis of the Ag-Cu binary phase diagram,the phase can be obtained as the?-Cu phase;The second is the white phase in the center of the weld,which is determined to be a solid solution of Ag-Cu and Ag-Sn with high Ag content by energy spectrum analysis.According to the analysis of the binary phase diagram of Ag-Cu,the phase is?-Ag phase;The third is a light gray structure with intermittent distribution.Judging from the mass fraction ratio,it may be a Cu-Sn solid solution dominated by Cu₃Sn.