Hardening and strain-ageing by vacancies and their aggregates in FeAl

Morris, David G.; Joye, J.C.; Leboeuf, M.

doi:10.1080/01418619408242530

Cited by 54 publications

(15 citation statements)

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“…The vacancy clusters in FeAl should be stable even at high temperature, because the vacancy binding energy is positive in FeAl. 9) Although the type of secondary defects due to vacancy clustering seems to depend on aluminum concentration in FeAl, 23) the pore formation interior to bulk has been reported only for Fe-43 mol%Al by Morris et al 24) The observation of the secondary defects is lacking in water-quenched FeAl for a higher aluminum concentration. Since the vacancy concentration of Fe-45 mol%Al water-quenched from 1273 K 16) is comparaal.…”

Section: Resultsmentioning

confidence: 98%

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: 98%

Nanoporous Surfaces of FeAl Formed by Vacancy Clustering

et al. 2002

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“…The high strength retained by the composites studied up to 250 8C contrasts with the behaviour of other Al-based composites or conventional aluminium alloys [16,17] that exhibit very high strength at room temperature which decreases rapidly above 200 8C. The mechanisms responsible for the deformation process at temperatures between 150 and 250 8C have been analysed on the basis of the equation [18] s y Z ð_ 3=AÞ 1=n expðQ=nRTÞ where s y is the yield stress of the material, 3 0 the strain rate, A is a microstructure dependent constant, T the absolute temperature, R the gas constant and Q the activation energy corresponding to the thermally-activated mechanism responsible for the deformation process.…”

Section: Analysis Of the Strengthening Mechanisms At High Temperaturementioning

confidence: 98%

Comparative study of Al-TiAl composites with different intermetallic volume fractions and particle sizes

Muñoz-Morris¹,

Rexach²,

Lieblich³

2005

Intermetallics

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A new family of Al-matrix composites containing g-TiAl intermetallic reinforcement particles has been processed by extruding aluminium and TiAl powders in different proportions up to 50% of the intermetallic. To modify the size and distribution of the intermetallic powders they were used in three different states, namely, atomised, and milled for 1 and 5 h. The yield strengths of the composites are very dependent on the volume fraction of the reinforcement and follow a Hall-Petch type relationship on the interparticle spacing. Much of the strength of the composites is retained up to temperatures of 250 8C, with an activation energy responsible for the deformation process measured as QZ96G5 kJ/mol for all materials, indicating that the high temperature deformation is controlled by diffusion along dislocations in the aluminium matrix. The plastic ductility is also dependent on the volume fraction of particles but is not much affected by the particle state. The composites containing 25% particles have higher ductilities, ranging between 9 and 12% at all temperatures and for all particle states. q

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“…[24] The anomand interactions of the dislocations are therefore required. [10] aly of the yield stress as a function of temperature in polyChromium and Nb additions are reported to increase the crystalline TiAl has been found by some authors [25,26] and ductility in TiAl, [11] while B is reported to reduce the grain not found by others. [27] The reason for this is mainly the growth during thermal treatments.…”

Section: Introductionmentioning

confidence: 75%

Influence of the temperature on the plastic deformation in TiAl

Parrini¹

1999

Metall Mater Trans A

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A new alloy, Ti-48.6Al-1.9Cr-1.9Nb-1B, with a near-equiaxed ␥ microstructure and with a lamellar microstructure is investigated by compression tests between 20 and 800 ЊC and transmission electron microscopy (TEM). The yield stress exhibits no anomaly as a function of the temperature, while an anomaly, related to strain hardening, is found at 400 ЊC in the hardening rate and the activation volume for both the lamellar and nonlamellar structure. Above 700 ЊC, a change in the deformation mechanism occurs and the material becomes remarkably softer. The TEM micrographs highlight the importance of ordinary dislocation motion for both structures at all temperatures. The comparison with previously reported TEM observations on single-phase TiAl alloys shows definitely that the density of ordinary dislocations is higher in the investigated two-phase TiAl alloy deformed at room temperature. Also, the presence of the lamellar interfaces drastically changes the mechanical properties of the alloy and the deformation mechanism. In contrast to the nonlamellar samples, superdislocations are rare, and twinning is very frequent in the lamellar structure.

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Hardening and strain-ageing by vacancies and their aggregates in FeAl

Cited by 54 publications

References 0 publications

Nanoporous Surfaces of FeAl Formed by Vacancy Clustering

Nanoporous Surfaces of FeAl Formed by Vacancy Clustering

Comparative study of Al-TiAl composites with different intermetallic volume fractions and particle sizes

Influence of the temperature on the plastic deformation in TiAl

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