Partition of alloying elements between γ(L1₂), η (DO₂₄), β (B2) and H(L2₁) phases in the Ni-Al-Ti base systems

Partitioning behaviour of alloying elements (V, Nb, Ta, Cr, Mo, W, Hf, Zr, Mn, Fe, Co, Cu, Al, Si) between the γ' (L1₂:Ni₃Al), η(DO₂₄:Ni₃Ti), β₁(B2: NiAl), β₂(B2: NiTi) and H(L2₁:Ni₂AlTi) phases in the Ni-Al-Ti base systems at 1100°C has been studied mainly by the diffusion couple method. It is confirmed that (1) in the cases of equilibria between the phases H and β₁ and H and β₂, the elements with large atomic size such as Ta, Nb and Hf prefer to partition to the Ti-rich H phase and, (2) in the cases of equilibria between the H, γ' and η phases, the bcc elements such as Zr, V and Cr prefer to concentrate into the H phase rather than into the γ' or η phases, and (3) in the case of equilibrium between the γ and the η phases, the elements with a large atomic size such as Ta, Zr, W, Hf, Nb and Mo prefer to partition to the η phase rather than to the γ' phase. It is suggested that the size factor and the lattice stability of the component elements have a significant effect on the relative stability of these intermetallic phases. These data on the partition behaviour of alloying elements in the Ni-Al-Ti base system are likely to prove useful for alloy design involving Ni-base superalloys.