Effect of Composition in Active Filler Metals in Joining of Alumina to Spheroidal Graphite Cast Irons

The effects of composition in active filler metals, brazing temperature and reaction layer on the shear strength of Al2O3-spheroidal graphite cast iron (FCD400) joints were studied using two types of active filler metals (type A and type B). The variation of microstructures of reaction products formed at the interface between Al2O3 and the active filler metals was investigated by scanning electron microscopy and auger electron microscopy. The Al2O3-FCD400 joints indicated the strong shear strength with the increasing brasing temperarures in the range of 1023∼1173K. The Al2O3-FCD400 joints showed shear strength to about 230∼240MPa, 243∼250MPa under the brazing condition at 1073∼1123K for 900s, 1123∼1173K for 900s respectively using two types of active filler metals (type A and type B). Increasing the thickness of the active filler metals from 0.05mm to 0.10mm resulted in decreasing shear strength of the joints by 15-30PMa. Two reaction layers Ti3.3 (Cu, Al)3.6 O2.7 , Ti4.7 (Cu, Al)3.1 O1.9 were formed in the interface between the active filler metals and Al2O3, depending on the composition in the active filler metals. The shear strength of Al2O3-FCD400 joints are attributed to the formation of these reaction layers.