Characterization of stress at a ceramic/metal jointed interface by the V(Z) technique of scanning acoustic microscopy

The interface and its vicinity of a ceramic/metal joint has been investigated with the help of the well-known V(z) curve technique of scanning acoustic microscopy. As is well known that the process of heating and then cooling dissimilar materials introduces considerable stress at and near the interface. In this report, the relationship between the residual stress and the surface wave velocity distributions was obtained first with the help of X-ray diffraction. Then, delaminations were introduced at the interface by the use of a micro-Vickers indentation apparatus. The V(z) curve technique was then used again to measure values for the surface acoustic wave velocity along the interface. The defective specimens showed significantly different patterns of residual stress. Thus, this study presents useful guidelines in discriminating between good and defective ceramic/metal joints with scanning acoustic microscopy emerging as a tool.