| Aiming at the problem of surface properties difference is large betweentraditional solder alloys and high-volume silicon carbide particles reinforcedaluminum matrix composite, as well as interfacial energy is too big to noteffectively wet, the topic anti-uses surface silicon carbide ceramic particles ofcomposites and ceramic property of aluminum matrix surface oxide film itself, todesign and prepare green low-melting composite glass solder (SnO-ZnO-P2O5glasssolder) with good compatibilities with surface of composites, to achieve theconnection of high-volume silicon carbide particle reinforced aluminum matrix(60vol.%SiCp/Al) composites under non-vacuum condition.The experimental results found that, SnO-ZnO-P2O5glass solder has goodwetting property on the surfaces of A1alloy and SiC and lays good foundation forwetting and spreading of SnO-ZnO-P2O5glass solder on the surface of60vol.%SiCp/Al composite, the measured wetting angle of SnO-ZnO-P2O5glasssolder on the surface of60vol.%SiCp/Al composite is15.3°. There is no generationof new interface compounds in microstructure of wetting interface, in interface place,alloy elements of base metal are dissolved to solder and solid solution is generated,the free energy of the system is decreased to promote the wetting of solder on thesurface of base metal. The wetting mechanism is analyzed to as solution-diffusionwetting in reactive wetting. Brazing process uses the method of high-temperaturepre-oxidation on the surface of composites, to make the surface form a layer of lowoxide, what significantly improved wetting properties of SnO-ZnO-P2O5glasssolder and SiCp/Al composite.There is no significant interfacial reaction layer when connecting60vol.%SiCp/Al composite by SnO-ZnO-P2O5glass solder in the air, Al and Mgelements in base metal are largely dissolved to the solder, generated ZnO-P2O5basedsolid solution and SnO-P2O5based solid solution in the interface, and obtained thejoints with perfect micro appearance and higher strength under the conditions ofbrazing temperature560℃, holding time30min and micro pressure6×10-3MPa.The study found that, the glass solder viscosity will be high, flow on the surface ofbase metal will be inadequate and resulting in residual porosity when the brazingtemperature is more lower and holding time is more shorter; the dissolution distancefrom base metal to solder will be increased when brazing temperature is higher andholding time is longer. Wild phase SiC particles will be exposed and seriously affectmechanical properties of joints because the alloy elements in Al alloy dissolve to solder in the interface.Although SnO-ZnO-P2O5glass solder gives good solution to the problem ofpoor wetting of traditional metal solder on the surface of SiCp/Al composite, but themechanical performance of joint is not so high due to glass solder’s strength is low,the difference between thermal expansion coefficient and base metal itself ofcomposite is larger, while it is easy to remain porosities in the soldering seam whenbrazing in the air. In the future, we can improve the mechanical properties of thesolder itself and improve thermal physics matching between solder and base metalthrough changing the properties of glass solder and preparing composite glass solder,so it is expected to obtain welded jointed with excellent performance. The studymethod of topic can also provide an innovative idea to connection of otherceramic-metal composites. |
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