Effects of X-ray beam collimation on the measurement of residual stress distribution in a Si3N4/steel joint.

Abstract

X-ray collimation and diffraction conditions were optimized to evaluate the detailed distribution of residual stress quantitatively around the ceramic/metal interface, and the results were applied to the Si3N4/Cu/steel system. The residual stress value increased and finally saturated as the collimation and irradiation area decreased in the Si3N4 region close to the interface of the joint. The normal stress value across the interface saturated below 0.2 mm2 to 240 MPa for Si3N4/t0.2 mm Cu/steel, and to 400 MPa for Si3N4/steel. It is recommended that φ0.1 mm collimation is suitable to evaluate its detailed distribution along the interface in which the irradiation area is 0.016-0.031 mm2. Several characteristic features of distribution were successfully observed along the joined interface of Si3N4/t0.2 mm Cu/steel having a lapped surface; first large tensile normal stresses at both edges, secondly the minimum stress points 1-2 mm inside the edge which was originated by stress relief through a localized plastic deformation of the Cu buffer, and thirdly the maximum normal stress across the interface in the center region of the specimen which had never been predicted and could be caused by the three dimensional effect of the joined plate.