Metal-metal composites (MeMeCs) manufactured by coextruding beta [Ni(Al,Ti)
], beta'[Ni2AlTi] and gamma'[Ni-3(Al,Ti)] show promise as high strength, he
at resistant materials. The best combination of strength and plasticity are
obtained by using a high fraction (0.8) of gamma' as the matrix phase comb
ined with equal fractions of beta and beta' reinforcement. Further improvem
ents in properties may be obtained by increasing the fracture strength of t
he matrix phase following the methods used in monolithic gamma' alloys, Bor
on additions are shown to lead to significant improvements in tensile fract
ure strength. The highest levels of plasticity were obtained in an MeMeC ma
terial which had a matrix composition designed to allow the more ductile ga
mma phase to precipitate in the gamma', as well as containing boron to incr
ease grain boundary cohesion. Fractography suggests that tensile failure oc
curs in this material in a much more ductile way, with evidence of local pl
astic deformation and a largely transgranular failure mode rather than the
intergranular fracture observed in the other MeMeC materials.