Phase Constituents and Compressive Yield Stress of Ni-Co Base Alloys

Phase constituents and compressive yield stress of Ni-Co base alloys have been investigated. The results showed that two-phases of γ and γ′ were the main constituents in all the alloys. Ni3Ti-type (η) phase was observed in the alloys with lower Co and Ti content (alloy20); while a new intermetallic (Ni,Co,Cr)3(Ti,Al) phase with a hexagonal structure was detected in the higher Co and Ti containing alloy(alloy50). At temperatures lower than 1023 K, the compressive yield stress increased with increasing Co content up to 28.6 mass% and Ti content up to 7.4 mass%, but decreased with more Co and Ti addition. At temperatures higher than 1273 K, all the alloys showed similar yield stress.