Matter transport in solids

Howard, Robert; Lidiard, A. B.

doi:10.1088/0034-4885/27/1/305

Cited by 456 publications

(157 citation statements)

References 198 publications

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“…This very comprehensive approach did not lead to a clear identification of how the structural, configurational, and vibrational effects individually contributed to vacancy properties, and the complexity of the treatment did not allow one to extract rules of thumb that might be extrapolated to other alloy systems. On the other hand, there are various lattice gas models that treat vacancies through Bragg-Williams or quasichemical approaches [14,[35][36][37][38][39][40][41] that are transparent enough to extract rules of thumb. But these studies suffer from a too simple representation of the energetics, such as including pairwise nearest neighbor interactions only, that are applicable to very few actual alloys.…”

Section: Introductionmentioning

confidence: 99%

Ab initioprediction of vacancy properties in concentrated alloys: The case of fcc Cu-Ni

Zhang

Sluiter

2015

Phys. Rev. B

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Vacancy properties in concentrated alloys continue to be of great interest because nowadays ab initio supercell simulations reach a scale where even defect properties in disordered alloys appear to be within reach. We show that vacancy properties cannot generally be extracted from supercell total energies in a consistent manner without a statistical model. Essential features of such a model are knowledge of the chemical potential and imposition of invariants. In the present work, we derive the simplest model that satisfies these requirements and we compare it with models in the literature. As illustration we compute ab initio vacancy properties of fcc Cu-Ni alloys as a function of composition and temperature. Ab initio density functional calculations were performed for SQS supercells at various compositions with and without vacancies. Various methods of extracting alloy vacancy properties were examined. A ternary cluster expansion yielded effective cluster interactions (ECIs) for the Cu-Ni-Vac system. Composition and temperature dependent alloy vacancy concentrations were obtained using statistical thermodynamic models with the ab initio ECIs. An Arrhenius analysis showed that the heat of vacancy formation was well represented by a linear function of temperature. The positive slope of the temperature dependence implies a negative configurational entropy contribution to the vacancy formation free energy in the alloy. These findings can be understood by considering local coordination effects.

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Section: Introductionmentioning

confidence: 99%

Ab initioprediction of vacancy properties in concentrated alloys: The case of fcc Cu-Ni

Zhang

Sluiter

2015

Phys. Rev. B

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“…In detail, the extremely high influence given by grain boundaries can be pointed out as the responsible for such high diffusion rates of aluminum, since their presence has been multiplied by secondary austenite precipitation within ferritic matrix. The thermal generation of lattice defects can be observed in the maximum value of the aluminum diffusion rate associated to the maximum value of soaking time of the annealing thermal treatment [35,52]. The sample annealed for 210 s/mm undergoes a static recovery phenomenon of the ferritic grains, decreasing the number of its internal δ/δ boundaries and defects; then, also the aluminum diffusion rate is strongly reduced [26,36].…”

Section: Discussionmentioning

confidence: 99%

Hot-Dip Aluminizing on AISI F55–UNS S32760 Super Duplex Stainless Steel Properties: Effect of Thermal Treatments

Ciuffini

Barella

Cecca

et al. 2017

Metals

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Abstract:The behavior of super duplex stainless steels AISI F55-UNS S32760 in hot-dip aluminizing process has been studied, investigating the influence of cold working and of different initial microstructures obtained through a preliminary thermal treatment. The microstructural features examined are the secondary austenite precipitation, the static recovery of ferrite and the thermal dissolution of austenite within ferritic matrix. The hot-dip aluminizing temperature has been optimized through sessile drop tests. The treatment has been performed at 1100 • C for 300 s, 900 s and 2700 s. A strong chemical interaction occurs, generating intermetallic compounds at the interface. Molten aluminum interacts exclusively with the ferritic phase due to its much higher diffusivity in this phase coupled with its marked ferrite-stabilizer behavior. Thus, the influence of cold working is not remarkable, since the strains are mainly allocated by austenitic phase. The diffusivity of aluminum increases due to lattice defects thermally generated and, mainly, to influence given by grain boundaries, multiplied by secondary austenite precipitation, which act as short-circuit diffusion paths. Ni and Cr contents in the ferritic matrix have an influence but not highly relevant. Then, the best starting condition of the super duplex stainless steel substrates, to obtain a thick interfacial layer, are the thermal annealing at 1080 • C for 360 s/mm after a solution thermal treatment at 1300 • C for 60 s/mm.

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“…This transport of heat is described by the heat of transport, Q * , which is the heat carried from the initial site to the final site. [1] Both Glover 7 and Malik [8][9] have used non-equilibrium thermodynamics 10 to develop general flux equations that can be combined with point defect information of specific oxides to predict oxidation rates. The general flux equation, from Malik 8-9 is:…”

Section: Theorymentioning

confidence: 99%

Effects of Temperature Gradients and Heat Fluxes on High-Temperature Oxidation

Holcomb

2008

Oxid Met

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The effects of a temperature gradient and heat flux on point defect diffusion in protective oxide scales were examined. Irreversible thermodynamics were used to expand Fick's first law of diffusion to include a heat flux term-a Soret effect. Oxidation kinetics were developed for the oxidation of cobalt and of nickel doped with chromium. Research is described to verify the effects of a heat flux by oxidizing pure cobalt in a temperature gradient at 900ºC, and comparing the kinetics to isothermal oxidation. No evidence of a heat flux effect was found.

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Matter transport in solids

Cited by 456 publications

References 198 publications

Ab initioprediction of vacancy properties in concentrated alloys: The case of fcc Cu-Ni

Ab initioprediction of vacancy properties in concentrated alloys: The case of fcc Cu-Ni

Hot-Dip Aluminizing on AISI F55–UNS S32760 Super Duplex Stainless Steel Properties: Effect of Thermal Treatments

Effects of Temperature Gradients and Heat Fluxes on High-Temperature Oxidation

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