The Evaluation of the Interparticle Spacing in Dispersion Alloys

Corti, C. W.; Cotterill, P.; Fitzpatrick, G. A.

doi:10.1179/095066074790137088

Cited by 82 publications

(21 citation statements)

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“…Since the particle area fraction and the volume fraction are identical for a polydispersed system of spheres [8,11], the macroscopic particle volume fraction, Φ, is also 0.115.…”

Section: Resultsmentioning

confidence: 99%

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Microstructural Characterization of Nodular Ductile Iron

Springer¹

2012

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“…Since the particle area fraction and the volume fraction are identical for a polydispersed system of spheres [8,11], the macroscopic particle volume fraction, Φ, is also 0.115.…”

Section: Resultsmentioning

confidence: 99%

“…Since no methods exist for transforming two-dimensional nearest neighbor distance distributions to a three-dimensional quantity, a relationship based on Corti et al [8] was used to determine the three-dimensional nearest neighbor distance from the particle volume fraction. The relationship for nearest neighbor distance is,…”

Section: Particle Field Analysismentioning

confidence: 99%

Microstructural Characterization of Nodular Ductile Iron

Springer¹

2012

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“…For 0.03 m alumina additions, 58 pct of the surface area was covered. Corti and Cotterill [8] used alumina particles smaller than 0.03 m, and the minimum amount employed was about 0.16 wt pct. This implies that more than 19 pct of the iron powder surface was covered.…”

Section: Discussionmentioning

confidence: 99%

“…This study used only the pressHowever, most previous studies indicated that inert oxides and-sinter process and concentrated on the effects of the caused an inhibition of sintering. [8][9][10][11] Corti and Cotterill [8] amount and size of alumina powders. The amount of alumina mixed ␥ alumina particles, which were smaller than 0.03 used ranged from 0.1 to 1.2 wt pct, and two sizes, 0.05 and m, with carbonyl iron powders by dry ball milling for 24 0.4 m, were compared.…”

Section: Introductionmentioning

confidence: 99%

Improved densification of carbonyl iron compacts by the addition of fine alumina powders

Hwang

2000

Metall Mater Trans A

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An investigation of the effect of alumina particles on the sintering behavior of a carbonyl iron powder compact was carried out in this study. Two different-sized alumina, 0.05 and 0.4 m, were added to the iron compact at amounts up to 1.2 wt pct. When 0.4 m alumina particles were added, no sintering enhancement was observed. But, in contrast to previous results reported in literature, the addition of 0.1 to 0.2 wt pct of 0.05 m alumina particles was found to improve the densification. With 0.1 wt pct, the sintered density increased from 7.25 to 7.40 g/cm 3 after the compact was sintered at 1350 ЊC for 1 hour in hydrogen. Dilatometric curves showed that alumina impeded the early-stage sintering of iron in the ␣ phase, but improved densification in the ␥ phase at high temperatures. These results, along with microstructural analysis, suggested that alumina particles exhibit dual roles; their physical presence blocks the diffusion of iron atoms, thus causing inhibition of sintering, while their grainboundary pinning effect prevents exaggerated grain growth of iron and helps densification. It follows that, depending upon the amount and size of the alumina powders, either an increase or decrease in the final sintered density can be obtained.

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“…From the formula for the nearest neighbor distance between randomly distributed dispersoid particles (ref. 14), it is deduced that the lamellar thickness t, for optimum dispersoid distribution is given by…”

Section: Model For Nonreactive Milling and Implicationsmentioning

confidence: 99%

Oxide-Dispersion-Strengthened Nickel Produced by Non-Reactive Milling

Arias¹

1976

Powder Metallurgy

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It is shown that oxide dispersion strengthened alloys can be produced by a postulated nonreactive milling mechanism whereby the dispersoid is trapped at the interface between welding metal powder particles. This interparticle welding is possible because, without a suitable and sufficiently vigorous chemical reaction between the metal powder particles and the milling fluid, no protective, weld-preventing reaction coating is formed on these particles. Using water as the nonreactive milling fluid, Ni -1. 8-vol % thoria and Ni -1. 8-vol % yttria alloys with 1093° C 9 tensile strengths ranging from 122. 3 to 141. 5 MN/m (17 900 to 20 500 psi) were produced by nonreactive milling. This investigation has shown that oxide dispersion strengthened nickel alloys can be produced by a postulated nonreactive milling mechanism. Nickel -1.8-volume-percent thoria and nickel -1.8-volume-percent yttria powders were milled for 640 hours using water as the milling fluid; samples of powders after various milling times were examined by electron microscopy; the amounts of dispersoids taken up by the nickel as a function of milling time were determined; and the high-temperature strengths of the consolidated alloys were obtained.The rate at which the yttria was kneaded into the nickel decreased with milling time; all the yttria was removed from the liquid in about 80 hours. Thoria was kneaded into the nickel at an approximately constant rate; all the thoria was removed from the liquid in about 145 hours. The milled powders were relatively coarse and nonpyrophoric. Micrographs showed them to be multilayered agglomerates of nickel lamellae welded together with the dispersoid trapped at the welded lamellar interfaces. For the nickelyttria run, the thicknesses of the lamellae varied from about 0. 5 to 0.06 micrometer after 46 and 640 hours milling time. Because lamellae stretch and become thinner with milling time, it is deduced that there is a minimum milling time required for optimum dispersoid distribution; this distribution cannot be improved by further milling.Because of the nonreactivity of nickel with water, nickel powder cakes on nickel balls and mills due to welding. However, the protective oxide coating that forms on the stainless-steel balls and mill surfaces, by reaction with water, prevents welding to the nickel powder during milling.The 1093° C ultimate tensile strengths of the ODS nickel alloys, about the same for nickel-thoria and nickel-yttria, range from 122. 3 to 141. 5 meganewtons per square meter. The 0.2 percent yield strengths range from 113.1 to 131. 0 meganewtons per square meter, and the elongations at fracture from 2. 7 to 5. 0 percent. These values compare favorably with those reported in the literature for nickel -1.8 volume percent thoria.Micrographs of the consolidated alloys show dispersoid sizes and distributions that are comparable to those of the best ODS nickel alloys reported in the literature.

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The Evaluation of the Interparticle Spacing in Dispersion Alloys

Cited by 82 publications

References 0 publications

Microstructural Characterization of Nodular Ductile Iron

Microstructural Characterization of Nodular Ductile Iron

Improved densification of carbonyl iron compacts by the addition of fine alumina powders

Oxide-Dispersion-Strengthened Nickel Produced by Non-Reactive Milling

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