| Summary: | 碩士 === 國立交通大學 === 機械工程系 === 88 === Ceramic materials have excellent properties, but their brittleness limits the range of the application, so it needs proper joining technique to promote the use of ceramic materials. Pre-metallization and active brazing process have been widely used in the joining of ceramic-ceramic or ceramic-metal materials. The microstructures of SiC/SiC joints brazed with commercial Ag68.8Cu27.6Ti4.5、home made Ag63.8Cu31.3Ti4.9、Ag59.4Cu26.4In12.5Ti1.7 filler metals and pre-coating Ti or Zr SiC brazed with AgCu filler metal were examined. The strength of the joints according to the four point test result was determined. Then the relationship between the microstructure and the strength of the joints was discussed.
The joining strength in this study is in the following order : commercial AgCuTi filler metal joints > home made AgCuTi filler metal joints > pre-coating Ti then brzaed with AgCu filler metal joints. The joints made with the AgCuInTi and pre-coating Zr then brazed with the AgCu filler metal have very poor join strength, they even break in the process of preparing the specimen.
Through the observation of the microstructure of the joints, it was found that the joints made by the commercial AgCuTi filler metal form two reaction layers TiC and Ti5Si3. Because the elements in the home made AgCuTi filler metal were not uniform, the reaction layer was not uniform and complete, mainly composed by the Ti and C reaction products. Joints made by the premetallization process did not have good bonding strength, because Ti, Zr coatings didn’t produce complete reaction layers. AgCuInTi filler metal formed a reaction layer compsed by Ti and Si. Although the reaction layer is quite complete, but the physical property of the reaction layer may affect the joining strength.
|
|---|
