X-ray determination of static displacements of atoms in alloyed Ni₃Al

Abstract

Single crystals of Ni3(A1, M) were grown by the Bridgman method, where M is Ti, V, Cr, Mn, Fe, Nb, Mo and Ta. The composition was controlled to be about NivsA120M5 so that the alloying element, M, substitutes mainly for A1. With these crystals conventional X-ray structural analysis was performed. The measured static displacements of atoms from the average lattice points depended largely on the alloying elements and varied in the range 0-00-0.13 A for Ni atoms and 0"09-0.18 A for AI atoms. It was found that these atomic displacements correlated well with the atomic radius of the alloying element, M. For example, when the atomic radius of M is larger than that of A1, the static displacements are large for the atoms in the A1 sublattice but small for the atoms in the Ni sublattice. By contrast, when the atomic radius of M is smaller than that of AI, the displacements are more enhanced in the Ni sublattice than in the AI sublattice. Thus, there is an interesting correlation between the atomic displacements in both the AI and Ni sublattices in the presence of alloying elements. This seems to be one of the characteristics of alloyed compounds with several sublattices.

Large area strain analysis using scanning transmission electron microscopy across multiple images

“…19 As a consequence, compressive strain would be introduced in the neighboring Ni sub-lattice for Cr rich atom columns. 20 These displacements have been indirectly observed previously using X-ray/neutron diffraction based methods, and a similar effect has recently been observed in a complex oxide solid solution using RevSTEM. 20,21 Further investigations are required to correlate chemistry with the degree of displacement but are beyond the scope of this work.…”

Lattice Site Occupancy in Ternary Ordered Ni3Al1-xFexAlloys Estimated by EXAFS

“…Several theoretical and experimental approaches to this problem was reported using different substitutional elements [3][4][5][6][7][8]. Three types of substitutional behavior in ordered NiAIX alloys can be distinguished, depending on the relative magnitude of Ni-X and ΑI-Χ interactions -the preferential substitution of Χ in: 1) Ni sites, 2) Α1 sites, 3) both sites.…”

“…The present work contributes to a research project aiming to study the Νi3Αl1-xFex system. Theoretical calculations [3,4] and some experimental evidences [5][6][7][8] suggest that the behavior of Fe does not indicate a strong preference to occupy only Ni or only Al sites; therefore, Fe should be classifled as having a substitutional behavior of the third type. Moreover, electron channeling enhanced microanalysis (ΑLCHEMI) [7] and theoretical considerations [4] indicate that this substitutional behavior of the third type elements is very sensitive to deviations from the stoichiometric composition.…”

Hf dopants in γ′–Ni3Al alloy

“…The atomic displacements, correlated with the atomic radius of the alloying element, are large for the atoms in the Al sublattice and small for the atoms in the Ni sublattice. 15,16 In this work, we present a series of TDPAC experiments and an ab initio study of the NQIs at the 181 Ta ion probe sites in the c 0 -Ni 3 Al-0.2 at. % Hf system.…”