Metal-metal composites (MeMeCs) manufactured by coextruding #beta#(Ni(Al,Ti)), #beta#'(Ni_2AlTi) and #gamma#'(Ni_3(Al,Ti)) show promise as high strength, heat resistant materials. The best combination of strength and plasticity are obtained by using a high fraction (0.8) of #gamma#' as the matrix phase combined with equal fractions of #beta# and #beta#' reinforcement. Further improvements in properties may be obtained by increasing the fracture strength of the matrix phase following the methods used in monolithic #gamma#' alloys. Boron additions are shown to lead to significant improvements in tensile fracture strength. The highest levels of plasticity were obtained in an MeMeC material which had a matrix composition designed to allow the more ductile #gamma# phase to precipitate in the #gamma#', as well as containing boron to increase grain boundary cohesion. Fractography suggests that tensile failure occurs in this material in a much more ductile way, with evidence of local plastic deformation and a largely transgranular failure mode rather than the intergranular fracture observed in the other MeMeC materials.
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