Alumina/carbon steel joint is performed with the direct brazing technique. In this case, residual stresses develop as the joint assembly is cooled from brazing temperature to room temperature. The residual stress distribution in alumina near interface is determined by XRD measurements and FEM(finite element method) analyses. XRD measurements are accomplished by a Ø 1mm collimated X-ray and the common package program (ANSYS 4.4A) is used to calculate the states of residual stresses. The results of XRD measurements are in good agreement with those of FEM analyses qualitatively.
Many effects of brazing alloy thickness on the level of residual stresses are investigated. The maximum tensile residual stresses on alumina surface near interface depend strongly on the thickness of brazing alloy. Three effects are considered to explain the dependence. The first is the effect of material properties-elastic modulus and thermal expansion coefficient mismatch. Secondly volume influence is introduced and the last but not negligible is one of the distance of the joining components. The experimental equation including above effects is obtained, which would be used to explain the changes of the maximum tensile residual stresses on alumina surface with brazing alloy thickness.
