Research On The Joining Process Of Al₂O₃ Ceramics By Using Bi₂O₃-B₂O₃-ZnO Glass Solder At Low Temperature

Alumina ceramics is a kind of structural ceramics which is widely used in microelectronic devices,aerospace,pharmaceutical and chemical industries due to its high strength,hardness and stability.However,it's difficult to manufacture complex alumina ceramic structural components because of the poor machinability,so welding is usually used in alumina ceramic components fabrication.Among kinds of welding methods,brazing and diffusion welding are commonly used in alumina ceramics joining.These two methods generally involve complicated processes,expensive equipment,and high residual thermal stress.In order to reduce the residual thermal stress and meet the demand of low costing and simple process,the article focused on the air joining of alumina ceramics at low temperature by using of Bi2O3-B2O3-ZnO glass solder with low softening point.Reliably joints were obtained by optimizing the process parameters and studying of the interfacial reaction between alumina ceramics and glass.The corresponding physical properties of Bi2O3-B2O3-ZnO glass were tested.The crystallization temperature and corresponding crystallization activation energy of Bi2O3-B2O3-ZnO glass were clarified through DSC test and corresponding kinetic calculations,which provided a theoretical basis for the selection of welding process parameters.The glass-forming property of Bi2O3-B2O3-ZnO glass and the CTE compatibility with alumina were determined by XRD and CTE tests.The wetting behavior of Bi2O3-B2O3-ZnO/Al2O3 system changing with temperature was studied.At about 620 ?,the system quickly changed from non-wetting state to wetting state,and the interface reaction layer of ZnAl2O4 was founded at the interface,so the wetting mechanism was contact reaction wetting.Alumina ceramics were joined with 50Bi2O3-30B2O3-20 ZnO glass,and the effects of process parameters on the microstructure and mechanical properties of the joints were clarified.When the joining temperature is lower than 625 ?,Bi38ZnO58 and Bi45BO69 crystallized during the cooling process of the joint;when the joint temperature is higher than 625 ?,the joint mainly contained glass and ZnAl2O4 react production.Maximum shear strength of the joints is 85 MPa when welded at 675? for 0 min.The failure mechanism of joints at different temperatures was studied.The fracture occurred mainly in the glass solder at low temperature.With the increase of temperature,the fracture gradually moved from the glass solder to the interface,and the joint welded at 725? was fractured from the base metal and the interface.