Prediction of the site ordering behaviours of elements in C15 NbCr2-based intermetallics by combining thermodynamic model with ab-initio calculation

The ordering behaviours of the transition metal elements in NbCr2-based alloys were predicted by combining thermodynamic model with ab-initio calculation. The predicted results show that for the ternary alloying elements in C15-type NbCr2-based alloy 64Cr–32Nb–4M (M = Cr, Hf, Mn, Mo, Nb, Ta, Ti, V, W or Zr), Mn atoms occupy only Cr sublattices (16d) and Hf, Ta, Ti and Zr atoms always prefer to occupy the Nb sublattices (8a). It is also found that the site preference of alloying elements Hf, Ta, Ti, Zr, or Mn are independent of the xCr/xNb (atomic ratio) and heat treatment temperature, while the site preferences of V, Mo or W depend on those. Present predicted results agree considerably with the available literatures, and some disagreements were also argued in this paper, i.e., in some literatures, alloying element V atoms always prefer to 16d sublattices and Ti atoms vary strongly with the alloy composition (xCr/xNb) and heat treatment temperature.