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The phase relation and microstructure of alloys based on the Ni 3 Al-Ni 3 Nb-Ni 3 V pseudo-ternary alloy system at 1273 and 1373 K were investigated by optical microscopy, X-ray diffraction, and scanning electron microscopy (attached with a wavelength dispersive spectroscope). There was no other intermediate phase besides L1 2 (Ni 3 Al), D0 a (Ni 3 Nb) and D0 22 (Ni 3 V). The phase fields of L1 2 (Ni 3 Al), D0 a (Ni 3 Nb) and D0 22 (Ni 3 V) have been shown to primarily depend upon the free electron concentration (e/a) of the constituent atoms. Among the three constituent intermetallic phases, one kind of three-phase relation (i.e. L1 2 -D0 a -D0 22 ) and three kinds of two-phase relations (i.e. L1 2 -D0 a , D0 a -D0 22 and L1 2 -D0 22 ) were found to exist at 1273 K. The prepared alloys exhibited widely different microstructures, depending on alloy composition and temperature. In the low Nb concentration region, dual multi-phase microstructures composed of L1 2 C D0 a CA1(/L1 2 CD0 22 ) were formed by a eutectic reaction. q

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Dual two-phase intermetallic alloys composed of Ni 3 X (X: Al and V) containing Nb were developed, on the basis of the Ni 3 Al-Ni 3 Nb-Ni 3 V pseudo-ternary alloy system. The dual two-phase intermetallic alloys were characterized by scanning electron and transmission electron microscopies. High-temperature compression and tension tests, and compression creep test were conducted. It was found that the dual two-phase intermetallic alloys show high yield and tensile strength with good temperature retention, accompanied with reasonable tensile ductility. The compression creep test conducted at high temperature showed lower creep rate in the dual two-phase intermetallic alloys than in conventional Ni-base superalloys. The obtained results are superior to the dual two-phase intermetallic alloys containing Ti.