Positron annihilation measurements of quenched-in defects in Ni

Troev, T.; Angelov, Ch.; Mincov, I.

doi:10.1016/0375-9601(89)90805-0

Cited by 5 publications

(7 citation statements)

References 10 publications

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“…Though being higher than the recommended value in Ref. [6], our prediction of E f for PM Ni is within the uncertainty of the experiments [33,35,98,99], including the most recent one using differential dilatometry [98] to measure directly the equilibrium vacancy concentration.…”

Section: Overall Behavior and Comparison With Experimentssupporting

confidence: 59%

“…In the light of this suggestion, the recommended value of E f in Ref [6] is 1.79 eV. The results from the recent experiments [35,36,98] are shown in Table IV. Though being higher than the recommended value in Ref.…”

Section: Overall Behavior and Comparison With Experimentsmentioning

confidence: 96%

“…Here we focus on fcc Fe and fcc Ni, which are the major constituents for the technologically important austenitic steels. At variation with the bcc-Fe case, experimental data on the vacancy concentration and the vacancy formation free energy are only available for the paramagnetic (PM) states of fcc Fe [29][30][31][32][33] and fcc Ni [6,[34][35][36], due to the low magnetic transition temperatures (67 K for fcc Fe [37] and 627 K for fcc Ni [38]). On the theoretical side, previous first principles investigations on the vacancy formation and diffusion properties in the PM regime were often informed by results on the ferromagnetic (FM) state of fcc Ni [39][40][41][42][43] and the nonmagnetic (NM) state in the case of fcc Fe [44][45][46].…”

Section: Introductionmentioning

confidence: 99%

“…Experiments 2.0 ± 0.2 [96] 1 .79 ± 0.1 [96] 1 .40 ± 0.15 [33] 1 .73 ± 0.07 [36] 1.81 ± 0.1 [97] 1 .74 ± 0.1 [97] 1 .7 ± 0.2 [32] 1 .7 ± 0.1 [35] 1.60 ± 0.15 [29] 1 .53 ± 0.15 [29] 1 .83 ± 0.14 [30] 1 .6 ± 0.1 [35] 1.56 ± 0.04 [98] 104406-6…”

mentioning

confidence: 97%

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Effects of magnetic excitations and transitions on vacancy formation: Cases of fcc Fe and Ni compared to bcc Fe

Fu²,

Schneider³

2021

Phys. Rev. B

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Vacancy is one of the most frequent defects in metals. We study the impacts of magnetism on vacancy formation properties in fcc Ni, and in bcc and fcc Fe, via density functional theory (DFT) and effective interaction models combined with Monte Carlo simulations. Overall, the predicted vacancy formation energies and equilibrium vacancy concentrations are in good agreement with experimental data, available only at the high-temperature paramagnetic regime. Effects of magnetic transitions on vacancy formation energies are found to be more important in bcc Fe than in fcc Fe and Ni. The distinct behavior is correlated to the relative roles of longitudinal and transversal spin excitations. At variance with the bcc-Fe case, we note a clear effect of longitudinal spin excitations on the magnetic free energy of vacancy formation in fcc Fe and Ni, leading to its steady variation above the respective magnetic transition temperature. Below the Néel point, such effect in fcc Fe is comparable but opposite to the one of the transversal excitations. Regarding fcc Ni, although neglecting the longitudinal spin excitations induces an overestimation of the Curie temperature by 220 K, no additional effect is visible below the Curie point. The distinct effects on the three systems are closely linked to DFT predictions of the dependence of vacancy formation energy on the variation of local magnetic-moment magnitudes and orientations.

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Section: Overall Behavior and Comparison With Experimentssupporting

confidence: 59%

Section: Overall Behavior and Comparison With Experimentsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 97%

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Effects of magnetic excitations and transitions on vacancy formation: Cases of fcc Fe and Ni compared to bcc Fe

Fu²,

Schneider³

2021

Phys. Rev. B

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“…electrical resistometry [26,28]. The authors of [26,28] obtain a vacancy migration enthalpy of 1.2 ± 0.2 eV, a vacancy formation enthalpy of 1.8 ± 0.2 eV, and an entropy factor of 0.45 k B .…”

Section: Annealing Out Of Quenched-in and Irradiation-induced Defectsmentioning

confidence: 99%

The influence of microstructure on the sintering process in crystalline metal powders investigated by positron lifetime spectroscopy: III. Nickel reduction powder

Staab

Krause‐Rehberg

Vetter

et al. 1999

J. Phys.: Condens. Matter

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The sintering process in compacts of nickel reduction powder is investigated by positron lifetime spectroscopy. Additionally, the lifetime data obtained are compared to the data on the recovery and recrystallization after plastic deformation caused by cold rolling or pressing, and on the annealing out of vacancy clusters caused by low-temperature electron irradiation. Due to the small grain sizes inside the powder particles at lower temperature, positrons annihilate at grain boundaries, leading to vacancy-cluster-like signals. At intermediate temperature, a surface signal is detected . This is in agreement with an effective powder-particle size of estimated from scanning electron microscopy. When sintering starts, i.e. above , the only detected defect signal, besides a small surface signal, stems from large-angle grain boundaries. At the intensive-shrinkage stage, there are contributions from different shrinkage mechanisms. The experimentally observed shrinkage rates can be explained by Coble creep which seems to dominate the material transport. Nabarro-Herring and dislocation creep play only minor roles in this system.

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Magnetochemical effects on phase stability and vacancy formation in fcc Fe-Ni alloys

Nastar

et al. 2022

Phys. Rev. B

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Positron annihilation measurements of quenched-in defects in Ni

Cited by 5 publications

References 10 publications

Effects of magnetic excitations and transitions on vacancy formation: Cases of fcc Fe and Ni compared to bcc Fe

Effects of magnetic excitations and transitions on vacancy formation: Cases of fcc Fe and Ni compared to bcc Fe

The influence of microstructure on the sintering process in crystalline metal powders investigated by positron lifetime spectroscopy: III. Nickel reduction powder

Magnetochemical effects on phase stability and vacancy formation in fcc Fe-Ni alloys

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