Study On Vacuum Brazing Of Al₂O₃Dispersion-strengthen Copper And T2Copper

Based on the development of spot welding electrode, the vacuum brazing process ofAl2O3dispersion-strengthen copper and copper T2is studied in this paper. The influenceof brazing filler and brazing process parameters on joint microstructure and properties isstudied by tensile test under ambient temperature, optical microscopy, scanning electronmicroscope (SEM) and energy disperse spectroscopy (EDS), etc. Based on compositefiller metal Ag-Cu-Ti+BAg72Cu, the effects of filler composition, holding time andpressure on joint microstructure and properties are studied. The results show:(1) when theholding time is too short, metallurgical action between filler and base metal is weak andthe bond is not firm. As holding time keeping longer, metallurgical action between fillerand base metal is completely, getting the ideal joints. But when holding time is too long,the Ag element in the filler metal severely infiltrates into the two side of base metal,causing the eutectic structure decreases gradually and disappear finally, and the Cu solidsolution becomes more and more, then holes appear in brazed joint, which seriouslyaffected the quality of joint. Under optimal parameters, the tensile strength of joint canreach to over189Mpa.(2) Under the condition of the same holding time, using0.1mmAg-Cu-Ti+0.1mm BAg72Cu,0.1mm Ag-Cu-Ti+0.2mm BAg72Cu and0.2mm Ag-Cu-Ti+0.2mm BAg72Cu different composite filler, due to the different effective concentrationof Ti elements, different effects on the structure and property of joint, the jointperformance under the0.1mm Ag-Cu-Ti+0.2mm BAg72Cu composite filler is better, themechanical properties of the joints is improved obviously, and the cost of this kind ofcomposite filler is lower.(3) Using the composite filler of0.1mm Ag-Cu-Ti+0.2mmcombined BAg72and apply0.75Kg weight to it, When the holding time was40min, thejoint strength can reach about150MPa. Under the pressure the microstructure of jointmore compact, along with the holding time longer, less solder capillary to dispersioncopper side infiltration, the welding seam is part of brazing material, to avoid the holes, inaddition to exert pressure has certain effect on weld seam, to avoid holes in the weld line,mechanical properties of joints was better than no pressure.(4) Under the same conditions,using the composite solder,the results showed that pressure has little effect on the jointmechanical properties, when the holding time last for40min, the joint strength is above150MPa.(5) Under different vacuum degree, studied the effect of vacuum degree on thejoint performance, the results show that: joint strength is higher under the (100-10-1Pa)vacuum conditions than in the (10-1-10-2Pa) vacuum conditions.