Residual stress estimation of a silicon carbide-Kovar joint

Residual stress of silicon carbide and Kovar is calculated using the elasto-plastic method and its validity is checked by the four-point bending test. Silicon carbide and Kovar (Fe-27% Ni-7% Co) are diffusion bonded using Al-10% Si alloy clad on a pure aluminium sheet at 883 K and 4.9 MPa under a vacuum condition. The non-linear structure analysis program (ADINA) is used for the stress estimation. It is found by the calculation that the maximum tensile stress, about 170 MPa, is generated in the silicon carbide close to the interlayer. In the bending test, the fracture of the joint is found to occur from the point where the maximum calculated tensile stress is generated, and the bending strength of the joint is 113 MPa. It becomes clear that the calculated stress and the measured strength of the joint is nearly equal to the strength of the silicon carbide itself (280 MPa). Therefore, it can be concluded that the stress estimation in this method indicates a good approximation of the practical residual stress of the joint.