Interfacial free energies, nucleation, and precipitate morphologies in Ni-Al-Cr alloys

Calculations and atom-probe tomographic experiments

Zugang Mao, Christopher Booth-Morrison, Chantal K. Sudbrack, Ronald D. Noebe, David N Seidman*

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The effects of Cr additions on the morphologies οf γ′(L1 2 ordered) precipitates are studied in three Ni-Al-Cr alloys utilizing atom-probe tomography (APT) and first-principles calculations. We find that Cr and Al share the same sublattice sites in the L1 2 -structure: Chromium partitions from the L1 2 structure into the disordered f.c.c. matrix for a driving force of 0.436 eV atom −1 . Mixing between the Ni 3 Al(L1 2 ) and Ni 3 Cr(L1 2 ) structures is energetically unfavorable based on first-principles quasi-random structure calculations. Interfacial Gibbs free energies of Ni/Ni 3 Al(L1 2 ), Ni/Ni 3 Cr(L1 2 ), Ni/Ni 3 Cr(DO 22 ), and Ni n (Al y Cr 1-y )/Ni 3 (Al x Cr 1-x )(L1 2 ) interfaces are calculated for the {100}, {110}, and {111} planes. The temperature dependencies of the interfacial Gibbs free energies are determined by including phonon vibrational entropies. The equilibrium interfacial Gibbs free energies are determined using concentration profiles as a function of aging time, obtained using APT. At early aging times, the initial values of the interfacial Gibbs free energies are higher with small Cr concentrations in the γ’ (L1 2 )-precipitates. With increasing aging time, the interfacial Gibbs free energies decrease with increasing Cr concentration and achieve equilibrium values after 16-h of aging at 873 K (600 °C) for the three Ni-Al-Cr alloys. From classical nucleation theory, the nucleation of metastable Ni 3 Cr(L1 2 ) is easier than Ni 3 Al(L1 2 ) at 873 K (600 °C). Ni 3 Cr(DO 22 ) is more difficult to nucleate than Ni 3 Cr(L1 2 ) and Ni 3 Al(L1 2 ) at 873 K (600 °C). The Cr additions to Ni-Al alloys have significant effects on the critical radius and critical net reversible work of nucleation. With increasing Cr concentration, Ni 3 (Al,Cr)(L1 2 ) requires the smallest critical net reversible work to form but has a larger critical size. An embryo of Ni 3 Cr(L1 2 ) only acts as a nucleant for mixed L1 2 Ni 3 (Al x Cr 1-x ). The morphology of Ni 3 (Al,Cr)(L1 2 ) precipitates transforms from cuboidal-to-spheroidal with increasing Cr concentration, in agreement with APT observations.

Original languageEnglish (US)
Pages (from-to)702-714
Number of pages13
JournalActa Materialia
Volume166
DOIs
StatePublished - Mar 1 2019

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Gibbs free energy
Free energy
Precipitates
Nucleation
Atoms
Aging of materials
Tomography
Experiments
Chromium
Entropy
Temperature

Keywords

  • Atom-probe tomography
  • First-principles calculations
  • Interfacial Gibbs free-energy
  • Phase partitioning
  • Phonon vibrational entropy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

Mao, Zugang ; Booth-Morrison, Christopher ; Sudbrack, Chantal K. ; Noebe, Ronald D. ; Seidman, David N. / Interfacial free energies, nucleation, and precipitate morphologies in Ni-Al-Cr alloys : Calculations and atom-probe tomographic experiments. In: Acta Materialia. 2019 ; Vol. 166. pp. 702-714.
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title = "Interfacial free energies, nucleation, and precipitate morphologies in Ni-Al-Cr alloys: Calculations and atom-probe tomographic experiments",
abstract = "The effects of Cr additions on the morphologies οf γ′(L1 2 ordered) precipitates are studied in three Ni-Al-Cr alloys utilizing atom-probe tomography (APT) and first-principles calculations. We find that Cr and Al share the same sublattice sites in the L1 2 -structure: Chromium partitions from the L1 2 structure into the disordered f.c.c. matrix for a driving force of 0.436 eV atom −1 . Mixing between the Ni 3 Al(L1 2 ) and Ni 3 Cr(L1 2 ) structures is energetically unfavorable based on first-principles quasi-random structure calculations. Interfacial Gibbs free energies of Ni/Ni 3 Al(L1 2 ), Ni/Ni 3 Cr(L1 2 ), Ni/Ni 3 Cr(DO 22 ), and Ni n (Al y Cr 1-y )/Ni 3 (Al x Cr 1-x )(L1 2 ) interfaces are calculated for the {100}, {110}, and {111} planes. The temperature dependencies of the interfacial Gibbs free energies are determined by including phonon vibrational entropies. The equilibrium interfacial Gibbs free energies are determined using concentration profiles as a function of aging time, obtained using APT. At early aging times, the initial values of the interfacial Gibbs free energies are higher with small Cr concentrations in the γ’ (L1 2 )-precipitates. With increasing aging time, the interfacial Gibbs free energies decrease with increasing Cr concentration and achieve equilibrium values after 16-h of aging at 873 K (600 °C) for the three Ni-Al-Cr alloys. From classical nucleation theory, the nucleation of metastable Ni 3 Cr(L1 2 ) is easier than Ni 3 Al(L1 2 ) at 873 K (600 °C). Ni 3 Cr(DO 22 ) is more difficult to nucleate than Ni 3 Cr(L1 2 ) and Ni 3 Al(L1 2 ) at 873 K (600 °C). The Cr additions to Ni-Al alloys have significant effects on the critical radius and critical net reversible work of nucleation. With increasing Cr concentration, Ni 3 (Al,Cr)(L1 2 ) requires the smallest critical net reversible work to form but has a larger critical size. An embryo of Ni 3 Cr(L1 2 ) only acts as a nucleant for mixed L1 2 Ni 3 (Al x Cr 1-x ). The morphology of Ni 3 (Al,Cr)(L1 2 ) precipitates transforms from cuboidal-to-spheroidal with increasing Cr concentration, in agreement with APT observations.",
keywords = "Atom-probe tomography, First-principles calculations, Interfacial Gibbs free-energy, Phase partitioning, Phonon vibrational entropy",
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Interfacial free energies, nucleation, and precipitate morphologies in Ni-Al-Cr alloys : Calculations and atom-probe tomographic experiments. / Mao, Zugang; Booth-Morrison, Christopher; Sudbrack, Chantal K.; Noebe, Ronald D.; Seidman, David N.

In: Acta Materialia, Vol. 166, 01.03.2019, p. 702-714.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Interfacial free energies, nucleation, and precipitate morphologies in Ni-Al-Cr alloys

T2 - Calculations and atom-probe tomographic experiments

AU - Mao, Zugang

AU - Booth-Morrison, Christopher

AU - Sudbrack, Chantal K.

AU - Noebe, Ronald D.

AU - Seidman, David N

PY - 2019/3/1

Y1 - 2019/3/1

N2 - The effects of Cr additions on the morphologies οf γ′(L1 2 ordered) precipitates are studied in three Ni-Al-Cr alloys utilizing atom-probe tomography (APT) and first-principles calculations. We find that Cr and Al share the same sublattice sites in the L1 2 -structure: Chromium partitions from the L1 2 structure into the disordered f.c.c. matrix for a driving force of 0.436 eV atom −1 . Mixing between the Ni 3 Al(L1 2 ) and Ni 3 Cr(L1 2 ) structures is energetically unfavorable based on first-principles quasi-random structure calculations. Interfacial Gibbs free energies of Ni/Ni 3 Al(L1 2 ), Ni/Ni 3 Cr(L1 2 ), Ni/Ni 3 Cr(DO 22 ), and Ni n (Al y Cr 1-y )/Ni 3 (Al x Cr 1-x )(L1 2 ) interfaces are calculated for the {100}, {110}, and {111} planes. The temperature dependencies of the interfacial Gibbs free energies are determined by including phonon vibrational entropies. The equilibrium interfacial Gibbs free energies are determined using concentration profiles as a function of aging time, obtained using APT. At early aging times, the initial values of the interfacial Gibbs free energies are higher with small Cr concentrations in the γ’ (L1 2 )-precipitates. With increasing aging time, the interfacial Gibbs free energies decrease with increasing Cr concentration and achieve equilibrium values after 16-h of aging at 873 K (600 °C) for the three Ni-Al-Cr alloys. From classical nucleation theory, the nucleation of metastable Ni 3 Cr(L1 2 ) is easier than Ni 3 Al(L1 2 ) at 873 K (600 °C). Ni 3 Cr(DO 22 ) is more difficult to nucleate than Ni 3 Cr(L1 2 ) and Ni 3 Al(L1 2 ) at 873 K (600 °C). The Cr additions to Ni-Al alloys have significant effects on the critical radius and critical net reversible work of nucleation. With increasing Cr concentration, Ni 3 (Al,Cr)(L1 2 ) requires the smallest critical net reversible work to form but has a larger critical size. An embryo of Ni 3 Cr(L1 2 ) only acts as a nucleant for mixed L1 2 Ni 3 (Al x Cr 1-x ). The morphology of Ni 3 (Al,Cr)(L1 2 ) precipitates transforms from cuboidal-to-spheroidal with increasing Cr concentration, in agreement with APT observations.

AB - The effects of Cr additions on the morphologies οf γ′(L1 2 ordered) precipitates are studied in three Ni-Al-Cr alloys utilizing atom-probe tomography (APT) and first-principles calculations. We find that Cr and Al share the same sublattice sites in the L1 2 -structure: Chromium partitions from the L1 2 structure into the disordered f.c.c. matrix for a driving force of 0.436 eV atom −1 . Mixing between the Ni 3 Al(L1 2 ) and Ni 3 Cr(L1 2 ) structures is energetically unfavorable based on first-principles quasi-random structure calculations. Interfacial Gibbs free energies of Ni/Ni 3 Al(L1 2 ), Ni/Ni 3 Cr(L1 2 ), Ni/Ni 3 Cr(DO 22 ), and Ni n (Al y Cr 1-y )/Ni 3 (Al x Cr 1-x )(L1 2 ) interfaces are calculated for the {100}, {110}, and {111} planes. The temperature dependencies of the interfacial Gibbs free energies are determined by including phonon vibrational entropies. The equilibrium interfacial Gibbs free energies are determined using concentration profiles as a function of aging time, obtained using APT. At early aging times, the initial values of the interfacial Gibbs free energies are higher with small Cr concentrations in the γ’ (L1 2 )-precipitates. With increasing aging time, the interfacial Gibbs free energies decrease with increasing Cr concentration and achieve equilibrium values after 16-h of aging at 873 K (600 °C) for the three Ni-Al-Cr alloys. From classical nucleation theory, the nucleation of metastable Ni 3 Cr(L1 2 ) is easier than Ni 3 Al(L1 2 ) at 873 K (600 °C). Ni 3 Cr(DO 22 ) is more difficult to nucleate than Ni 3 Cr(L1 2 ) and Ni 3 Al(L1 2 ) at 873 K (600 °C). The Cr additions to Ni-Al alloys have significant effects on the critical radius and critical net reversible work of nucleation. With increasing Cr concentration, Ni 3 (Al,Cr)(L1 2 ) requires the smallest critical net reversible work to form but has a larger critical size. An embryo of Ni 3 Cr(L1 2 ) only acts as a nucleant for mixed L1 2 Ni 3 (Al x Cr 1-x ). The morphology of Ni 3 (Al,Cr)(L1 2 ) precipitates transforms from cuboidal-to-spheroidal with increasing Cr concentration, in agreement with APT observations.

KW - Atom-probe tomography

KW - First-principles calculations

KW - Interfacial Gibbs free-energy

KW - Phase partitioning

KW - Phonon vibrational entropy

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