High-temperature atomic defect properties and diffusion processes in intermetallic compounds

Schaefer, H.‐E.; Frenner, Karsten; Würschum, Roland

doi:10.1016/s0966-9795(98)00121-6

Cited by 67 publications

(42 citation statements)

References 40 publications

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“…The experimental data for thermal vacancy formation, determined by time-differential length change measurements only experimental value of 0.68 eV for the effective enthalpy of formation of thermal vacancies in stoichiometric B2-for Ni 0.47 Al 0.53 [32] and indicated in Figure 7, agree fairly well with the model predictions. The value for the effective NiAl, determined from differential, thermal-expansion measurements, [27] is in excellent agreement with the data calcuenthalpy of formation of thermal vacancies calculated from the present model at x Al ϭ 0.53 (1.98 eV) is close to the lated from the present model (0.66 eV, Table V).…”

Section: Resultssupporting

confidence: 73%

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Thermodynamics of B2 intermetallic compounds with triple defects: a Bragg-Williams model for (Ni,Co)Al

Breuer¹,

Sommer

Mittemeijer³

2001

Metall Mater Trans A

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Applying the Bragg-Williams approximation, a pair interaction model has been developed for describing the composition and temperature dependence of thermodynamic properties of ternary intermetallic B2 phases. Taking the activities and the integral enthalpies of formation as input data, values for the enthalpy and the entropy of bonds between atoms have been obtained. An analytical expression has been derived for the dependence of the concentration of point defects (vacancies and antistructure atoms) on composition and temperature. The model has been applied successfully to the available experimental data for the Ni-Al, Co-Al, and Ni-Co-Al systems. It has been shown that the values calculated accordingly for the effective enthalpy (and entropy) of formation of vacancies agree well with those from experimental observations and theoretical ab initio calculations.

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Section: Resultssupporting

confidence: 73%

“…vacancies for the pure, binary phases B2-NiAl and B2-CoAl agree well with the values reported in literature. [27,[30][31][32][33][34] The…”

Section: Resultsmentioning

confidence: 99%

Thermodynamics of B2 intermetallic compounds with triple defects: a Bragg-Williams model for (Ni,Co)Al

Breuer¹,

Sommer

Mittemeijer³

2001

Metall Mater Trans A

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“…Secondly, previous positron lifetime studies on single-crystalline D0 3 -Fe 3 Si have shown that stoichiometric as well as nonstoichiometric compositions are free of structural vacancies 18 and that nonequilibrium vacancies, which for example are introduced by electron irradiation, anneal out even at ambient temperature. 21 The absence of a lifetime component smaller than the free lifetime f ͑Table I͒ indicates saturation trapping of positrons, which is reasonable because the mean positron diffusion length in metal crystals (L ϩ Ϸ100 nm) is much larger than the grain size and the positrons therefore arrive at the interfacial traps with high probability.…”

Section: Resultsmentioning

confidence: 97%

“…100 nm diameter͒ and in coarse-grained material ͑Table II͒. Since self-diffusion in Fe 3 Si is mediated by vacancies, 21 we may therefore assume that the tracer diffusion characteristics for monocrystalline Fe 3 Si also pertain to Fe 3 Si nanocrystalllites of (Fe 3 Si) 95 Nb 5 . The diffusion lengths of either Fe or Si and Ge at 650 K ͑the mean temperature of the ordering process͒ were estimated from tracer diffusion data ͑see Ref.…”

Section: Correlation Between Ordering and Thermal Vacancy Charactementioning

confidence: 99%

Thermal vacancy formation andD03ordering in nanocrystalline intermetallic(Fe3
Pasquini
¹
,
Rempel
²
,
Würschum
³

et al. 2001
Phys. Rev. B
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The correlation between thermal vacancy characteristics and D0 3 ordering in ball-milled nanocrystalline (Fe 3 Si) 95 Nb 5 was studied by combined measurements of x-ray diffraction and positron annihilation. Structural stabilization due to grain boundary segregation of Nb enables high-temperature positron lifetime measurements up to 1023 K from which vacancy formation parameters identical to those in single-crystalline D0 3 Fe 3 Si are deduced. Measurements of coincidence Doppler broadening show that prior to the onset of thermal defect formation in the nanocrystallites, positrons are annihilated in Nb-enriched grain boundaries. The D0 3 ordering of the initially disordered Fe 3 Si nanocrystallites is discussed on the basis of the thermal vacancy characteristics and self-diffusion behavior.

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“…% Al, the type of defects at low temperatures are typically mono-vacancies. Figure 6b [59][60][61][62] shows the changes of the equilibrium vacancy concentration (C v ) of samples with different Al contents at different temperatures based on the experimental approaches. Obviously, the increase of either temperature or Al content will increase C v .…”

Section: Point Defects In the Super Cellsmentioning

confidence: 99%

A Review on the Properties of Iron Aluminide Intermetallics

2016

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Iron aluminides have been among the most studied intermetallics since the 1930s, when their excellent oxidation resistance was first noticed. Their low cost of production, low density, high strength-to-weight ratios, good wear resistance, ease of fabrication and resistance to high temperature oxidation and sulfurization make them very attractive as a substitute for routine stainless steel in industrial applications. Furthermore, iron aluminides allow for the conservation of less accessible and expensive elements such as nickel and molybdenum. These advantages have led to the consideration of many applications, such as brake disks for windmills and trucks, filtration systems in refineries and fossil power plants, transfer rolls for hot-rolled steel strips, and ethylene crackers and air deflectors for burning high-sulfur coal. A wide application for iron aluminides in industry strictly depends on the fundamental understanding of the influence of (i) alloy composition; (ii) microstructure; and (iii) number (type) of defects on the thermo-mechanical properties. Additionally, environmental degradation of the alloys, consisting of hydrogen embrittlement, anodic or cathodic dissolution, localized corrosion and oxidation resistance, in different environments should be well known. Recently, some progress in the development of new micro-and nano-mechanical testing methods in addition to the fabrication techniques of micro-and nano-scaled samples has enabled scientists to resolve more clearly the effects of alloying elements, environmental items and crystal structure on the deformation behavior of alloys. In this paper, we will review the extensive work which has been done during the last decades to address each of the points mentioned above.

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High-temperature atomic defect properties and diffusion processes in intermetallic compounds

Cited by 67 publications

References 40 publications

Thermodynamics of B2 intermetallic compounds with triple defects: a Bragg-Williams model for (Ni,Co)Al

Thermodynamics of B2 intermetallic compounds with triple defects: a Bragg-Williams model for (Ni,Co)Al

Thermal vacancy formation andD03ordering in nanocrystalline intermetallic(Fe3
Pasquini
¹
,
Rempel
²
,
Würschum
³

et al. 2001
Phys. Rev. B
Self Cite
18
1
11
0
View full text Add to dashboard Cite

A Review on the Properties of Iron Aluminide Intermetallics

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High-temperature atomic defect properties and diffusion processes in intermetallic compounds

Cited by 67 publications

References 40 publications

Thermodynamics of B2 intermetallic compounds with triple defects: a Bragg-Williams model for (Ni,Co)Al

Thermodynamics of B2 intermetallic compounds with triple defects: a Bragg-Williams model for (Ni,Co)Al

Thermal vacancy formation andD03ordering in nanocrystalline intermetallic(Fe3Pasquini1, Rempel2, Würschum3 et al. 2001Phys. Rev. BSelf Cite181110View full textAdd to dashboardCite

A Review on the Properties of Iron Aluminide Intermetallics

Contact Info

Product

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About

Thermal vacancy formation andD03ordering in nanocrystalline intermetallic(Fe3
Pasquini
¹
,
Rempel
²
,
Würschum
³

et al. 2001
Phys. Rev. B
Self Cite
18
1
11
0
View full text Add to dashboard Cite