STRUCTURAL FEATURES TO RELAX THERMAL-STRESS AT METAL CERAMIC JOINED INTERFACE

Direct metal/ceramic interface free of a reaction product layer and the atomic ledge structure aligned parallel to the trace of one of the slip planes of the metal was designed in niobium/alunima. Such interface should accommodate the thermal stress at high temperatures by nonconservative motion of the ledge involving the growth of ceramic side during cooling of the joined piece as solid solubilities of the ceramic components in metal decrease with the temperature. At lower temperatures where the nonconservative ledge motion is frozen, conservative motion of misfit dislocations results in stress concentration against the now immobile ledge and the stress may be relaxed by the emission of lattice dislocations into metal matrix.