Chromium and tantalum site substitution patterns in Ni3Al(L12) γ′-precipitates

Abstract

The site substitution behavior of Cr and Ta in the Ni 3 Al ͑L1 2 ͒-type ␥Ј-precipitates of a Ni-Al-Cr-Ta alloy is investigated by atom-probe tomography ͑APT͒ and first-principles calculations. Measurements of the ␥Ј-phase composition by APT suggest that Al, Cr, and Ta share the Al sublattice sites of the ␥Ј-precipitates. The calculated substitutional energies of the solute atoms at the Ni and Al sublattice sites indicate that Ta has a strong preference for the Al sites, while Cr has a weak Al site preference. Furthermore, Ta is shown to replace Cr at the Al sublattice sites of the ␥Ј-precipitates, altering the elemental phase partitioning behavior of the Ni-Al-Cr-Ta alloy.

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

“…The average width of the c regions between c 0 , also known as c channels, is 30-40 nm. Atomic-resolution EDS, in Figure 1(b), reveals that Cr predominantly occupies the Al sub-lattice in the c 0 phase, in agreement with recent atom probe tomography experiments 15,16 and first-principles calculations. 17 At the atomic scale, a representative c 0 /c interface is shown in Figure 1(c), where the two regions can be distinguished by the presence of the ordered Al/Cr sub-lattice atom column intensities (dark).…”

Effects of alloying elements on elastic properties of Ni3Al by first-principles calculations

“…Cr, Hf and Zr substitute for the Al sublattice sites while Pt substitutes for Ni sublattice sites. Experimentally, it is observed that Cr substitutes preferentially at the Al sublattice sites [37] and other first-principles studies show the same results [12,13,37]. The site preference of Y in L1 2 $Ni 3 Al is not studied before but based on the same approach its preference for the Al sublattice sites is expected.…”

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

“…However, our experimental observations show that for the case of these precipitates created using a cooling rate of 10K/min, Al content of γ increases as the precipitates get smaller, from 12.5 at.% in secondary γ precipitates with diameters of ∼230 nm, to 15.5 at.% in the smallest tertiary γ (∼25 nm). In contrast, the experimentally measured 25 and Ni 74 Al 26 , respectively. 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.…”

“…For the more complex case of RR1000 nickel-based superalloy, the chemistry of the γ phase is generally given as (Ni, Co, Cr, Mo) 3 (Al, Ti, Ta, Hf. The elements Al, Ti, Ta and Hf, are generally assumed to substitute into the β-sublattice, while Ni, Co, Cr, and Mo occupy the α-sublattice as predicted by first principle calculations [20][21][22][23][24][25]. Herein Hf is not found to be present at measurable levels in the precipitate size range considered in this work.…”