Residual stress distribution as a function of depth in graphite/copper brazing joints via X-ray diffraction

The residual stress distributions as a function of depth in three different graphite/copper brazing joints: with no interlayer, with a copper interlayer and with a niobium interlayer are measured via X-ray diffraction by transmission geometry. The residual stress in all the joints is found to be generally compressive and increasing from the surface to the interface. Copper and niobium interlayers are both effective in alleviating the residual stress in the joint and the stress value in the joint with a niobium interlayer appearing to be the lowest. The strength of the joint is demonstrated to be closely related to the residual stress and the fracture position of the joint corresponds well with the highest residual stress.