Thermal residual stresses near interface brazing aluminia matrix composite to metal

The chemical reaction of the composite with the brazing alloy takes place and the reaction layer,composed of TiO,TiC and so on,forms on the composite surface when SiC_w/Al₂O₃ composite is brazed to metals using Ag-Cu-Ti brazing filler alloy.The thermal residual stresses near the composite/reaction layer interface were calculated by finite element method.The results have shown that the residual stresses near the interface change abruptly,and the highest tensile stress appears at the intersection of the whisker,matrix and reaction layer.High compressive stresses develop in the whisker and on its surface,while the Al2O3 matrix is mainly subjected to the tensile stress perpendicular to the interface.The high tensile stress parallel to the interface exists at the whisker/reaction layer interface and in TiC near the interface,at which failure occurs easily when shear force is applied.Microstructure of the interface region and shear fracture surface of the brazed joints are observed by transmission electron microscope and scanning electron microscope,and the phenomena are analyzed from the calculated results.