Voids formed in quenched and annealed NiAl

Epperson, J. E.; Gerstenberg, Kurt; Berner, D.; Kostorz, G.; Ortiz, Celina R.

doi:10.1080/01418617808239252

Cited by 49 publications

(8 citation statements)

References 15 publications

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“…The concentration of supersaturated thermal vacancies can be controlled by changing cooling rate and aluminum content, which would govern the size and density of the pores based on the particular an- ble to that of the as-spun ribbons, we may be able to observe the pore formation as well as nanoporous surfaces in waterquenched, bulk FeAl in the higher aluminum concentration range. The pore formation interior to bulk has been observed in water-quenched B2-type NiAl [25][26][27][28][29] and CoGa, 30) and the formation mechanism has been often discussed for NiAl with relating to impurities. [25][26][27][28][29] Therefore, the nanoporous surface formation should be possible in other B2-ordered alloy systems.…”

Section: Resultsmentioning

confidence: 99%

“…The pore formation interior to bulk has been observed in water-quenched B2-type NiAl [25][26][27][28][29] and CoGa, 30) and the formation mechanism has been often discussed for NiAl with relating to impurities. [25][26][27][28][29] Therefore, the nanoporous surface formation should be possible in other B2-ordered alloy systems. The mechanism responsible for the nanoporous surface formation will be discussed a great deal using recent advanced microscopic techniques such as field emission scanning microscopy (FE-SEM), scanning probe microscopy (SPM), low energy electron microscopy (LEEM) and so on hereafter.…”

Section: Resultsmentioning

confidence: 99%

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Nanoporous Surfaces of FeAl Formed by Vacancy Clustering

et al. 2002

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Numerous thermal vacancies are frozen into FeAl B2-ordered alloy ribbons by a conventional rapid-solidification technique. Through heat treatment at 723 K, clustering of the supersaturated vacancies generates a large number of nanopores, particulary near surfaces, thus creating nanoporous surfaces. The nanoporous surface structure was confirmed by scanning electron microscopy and atomic force microscopy. The behavior of this vacancy clustering was examined by differential scanning calorimetry. An exothermic, irreversible peak, probably due to vacancy clustering, was observed around 800 K, giving an activation evergy of about 1.17 eV. The nanopore formation was also observed by in-situ heating experiments in a transmission electron microscope. The pores have specific morphology and crystallography with pore surfaces faceting toward {100} planes. These results suggest that the vacancy clustering is a unique process which enables us to efficiently make nanoporous surfaces.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Nanoporous Surfaces of FeAl Formed by Vacancy Clustering

et al. 2002

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“…The use of polycrystals, however, leads to spherical averaging of this pattern and thus to a considerable loss of information. For this reason, measurements have been performed more frequently in recent years on single crystals using a two-dimensional (2D) positionsensitive detector (Epperson, Gerstenberg, Berner, Kostorz & Ortiz, 1978;Kostorz, 1983;Calderon & Kostorz, 1990;Dubey, SchOnfeld & Kostorz, 1991;Paris, 1992;.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of 3D small-angle scattering from non-spherical particles in single crystals

Fratzl¹,

Langmayr²,

Paris³

1993

J Appl Cryst

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Three-dimensional small-angle scattering is discussed as a tool for investigation of anisometric particles in single-crystalline alloys. The measurement and evaluation methods take advantage of the well defined orientation relation between the precipitates and the matrix in alloys. The determination of shape, size and orientation of precipitates from the scattering in several planes of reciprocal space is discussed for the example of ellipsoids and plates. Shape and orientation of ellipsoids with small aspect ratio can be determined by deviations of the scattering intensity from spherical symmetry in certain planes of reciprocal space. Particle size is obtained from one-dimensional slices along certain directions. The small-angle scattering of plate-like particles with large aspect ratio is concentrated along radial streaks in reciprocal space. Slices along and across these streaks allow the determination of the plate thickness as well as size and aspect ratio of the plate surface. In addition, the evaluation of such 'off-center" slices provides a resolution enhancement of almost one order of magnitude compared to the conventional Guinier method applied to spherically averaged data.

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“…More recent measurements by Kogachi et al [3] have shown that the two other possible point defects, Al vacancies and Al Ni antisite defects, do exist in substantial numbers but that the Bradley and Taylor model is essentially correct. The concentrations of Ni vacancies in Al-rich alloys may be exceptionally high [4], up to 9 £ 10 22 . In addition to constitutional vacancies, thermal vacancy concentrations are also much higher than in pure metals.…”

Section: Introductionmentioning

confidence: 99%