Interdiffusion in ternary Ni3Al/Ni3Al-X diffusion couples with X=Cr, Fe, Nb and Ti

On the diffusion mechanisms of fine-scaleγ′ in an advanced Ni-based superalloy

“…All data has been extended from 6.7 × 10 −4 K −1 (1500 K) to 13 × 10 −4 K −1 (770 K) using Arrhenius curves and assumes a dilute solid solution. The data was obtained by summarizing results from references [8][9][10][11][12]. Current diffusivity data for Ta and Hf in γ was only available at 1470 K so their temperature dependence could therefore not be predicted.…”

“…We have summarised the reported interdiffusion coefficients for the different alloying elements in γ and γ phases [8][9][10][11][12] as shown in Fig. 5.…”

“…Thus Al, Ti and Ta are expected to be confined to the β-sublattice while Cr, Co and Mo diffuse only via the α-sublattice. Aluminium's anomalous behaviour has recently been explained using antisitebridge diffusion [10,11,27]. Aluminium can therefore diffuse preferentially within the β-sublattice via the α-sublattice, which enhances the diffusivity of Al in the γ precipitates at low temperature.…”

“…Faster solution cooling regimes result in higher nucleation rates and limited coarsening of γ due to the reduced time available for diffusion of γ stabilising elements at the later stages of cooling. The complexity of γ formation over a wide range of temperatures and cooling rates a Corresponding author: sarah.haigh@manchester.ac.uk in combination with the different diffusion rates of γ stabilisers in Ni [8][9][10][11][12] mean that the chemistry of γ is likely to vary within different sizes of precipitate and for different PSDs.…”

Diffusion of Al and Al-Substituting Elements in Ni₃Al at Elevated Temperatures

“…However, this phase in a pure binary form shows poor high-temperature creep strength and this strength can be improved by alloying. The elements replacing Al in Ni 3 Al, such as Ti, Nb, Ta etc. strengthen the £ A phase and thus contribute in strengthening the superalloys, whereas the Ni substituting elements (Co, Fe, Cr etc.)…”