DEFORMATION OF DUCTILE BRAZE LAYER IN A JOINT ELEMENT UNDER CYCLIC THERMAL LOADS

The structural lifetime of a brazed joint is affected by the plastic b ehavior of ductile filler metal. In this work, elastoplastic analysis is performed on a CFC/Cu/TZM bonded joint for different thermal loadin g cases. The evolution of strains in the braze layer during the brazin g process is analyzed. It is shown that the temperature dependence of the flow curves exerts considerable influence on the deformation behav ior of the filler metal interlayer. The deformation characteristics of the braze layer under thermal cycling are investigated. The effect of thermal gradient on the plastic deformation of the braze is discussed . The fatigue lifetime of the copper braze layer is estimated. High he at flux (HHF) cycling tests are conducted on a CFC/Cu/TZM brazed joint in an electron beam facility. The microstructure of the deformed copp er braze is presented. Th-flow morphologies and corresponding slip mec hanisms are discussed. (C) 1998 Elsevier Science S.A.