EVALUATION OF THE STRENGTH OF DIFFUSION-BONDED JOINTS IN CONTINUOUS FIBER-REINFORCED METAL-MATRIX COMPOSITES

SiC continuous fiber reinforced Ti-6Al-4V composites with various fibe r volume fractions were fabricated by the vacuum hot pressing process and were joined to a Ti-6Al-4V alloy plate by solid state diffusion bo nding processes. The matrix alloy was perfectly joined to the Ti-6Al-4 V plate within the bonding condition. The joint strength decreased wit h increasing fiber volume fraction. The joint strength was not directl y proportional the matrix area fraction. A joint efficiency over 90% c ould be obtained when the fiber volume fraction was less than 30%. The SiC fibers were debonded from the matrix and cylindrical defects were formed at the end of the fiber under tensile stress. The defects prod uced a triaxial stress state at the matrix alloy and thus higher joint strengths than the values simply calculated from the area fraction of the matrix at the bending interface. The composite was transient liqu id phase bonded to itself using Ti-Cu-Zr filler metal. The joint stren gth was degraded using thin interlayer less than 80 mu m thick. An int erlayer thickenss over 80 um was found to be necessary to obtain a sou nd joint. (C) 1997 Elsevier Science S.A.