Morphologie de l'eutectique orienté CoCoAl et influence d'une addition de nickel

Hubert, J.C.; Kurz, W.; Lux, B.

doi:10.1016/0022-0248(73)90167-x

Cited by 11 publications

(1 citation statement)

References 11 publications

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“…Hence less b phase will form. On the other hand it may explain why no b-c eutectic has been observed and has not formed by cooperative crystallization although it will easily form regular eutectic structures at "low" growth rates [33]. Both phases crystallize separately as single grains instead as soon as high solidification rates are involved.…”

Section: Concomitant Effects On the Microstructural Evolutionmentioning

confidence: 98%

Investigation of an as-sprayed NiCoCrAlY overlay coating - microstructure and evolution of the coating

Fritscher¹,

Lee

2005

Materials and Corrosion

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A low pressure plasma sprayed (LPPS) NiCoCrAlY aircraft turbine blade overlay coating was investigated in the as-sprayed condition by X-ray diffraction (XRD) and analytical transmission electron microscopic (TEM) techniques. c-Ni, b-NiAl and c 0 -Ni 3 Al phases were identified by XRD showing predominant c phase at the expense of b phase if compared to the fully processed state with c and b at about equal portions. Besides grains of c-Ni and b-NiAl, amorphous metallic grains and Cr-rich oxides were found by TEM. Close to the surface to the atmosphere c 0 -Ni 3 Al phase was localized in composite grains with an off-plane oriented c-c 0 fibrous eutectic structure. They were neighbored by amorphous metallic grains.The evolution of these structures is discussed within the scope of crystal growth behavior. The dominant occurrence of face-centered cubic at the expense of body-centered phases observed in assprayed coatings is attributed to their higher growth rates on quenching. Also benefiting from rapid growth the c-c 0 fibrous eutectic grains will form, hereby relying on essentially binary phase compositions of highly extended solubility ranges. Accumulation of alloy constituents like Cr and Ti by segregation to the growth front is considered to pave the way for the evolution of amorphous grains at the coating surface on top of c-c 0 grains. The potentials of the microstructures in service are addressed.

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Section: Concomitant Effects On the Microstructural Evolutionmentioning

confidence: 98%

Investigation of an as-sprayed NiCoCrAlY overlay coating - microstructure and evolution of the coating

Fritscher¹,

Lee

2005

Materials and Corrosion

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Predictability of Eutectic Microstructures

Fritscher¹

1997

Materialwissenschaft Werkst

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Dedicated to Prof. Wolfgang Bunk on the occasion of his 70th birthdayThe interphase spacings h in the microstructures of most binary and pseudobinary ,,normal" metallic eutectics can roughly be quantified with regard to their respective solidification rates v according to a general relationship h2 . v = constant the constant being commonly between IO-'"and lo-'' cm3sc1. The designation ,,normal" relates to similar degrees of undercooling of either phase on a plain-front solidification process at variance with anomaleous eutectics which solidify at different degrees of undercooling in an uncoupled or weakly-coupled manner. The ,,constant", however, is an individual value for each eutectic system. It is lowest for ,,simple" eutectics forming no intermetallic compounds and having low terminal solid solutions. The constant is raised for systems by 3 orders of magnitude or more if extensive terminal solid solutions are present. A closer fit for deliberate nor-mal eutectics is presented in this pragmatic approach if the concentration differences between the terminal phases in eutectics ACE [at%] are attributed to them as a square term according to h2The data based on this relation still show some scatter but they are grouping to distinct material families e. g. to Pb-, Agor Al-based eutectics. The remanent differences are estimated to disappear as soon as the relation is extended by the interdiffusion coefficient D according to{cm5 . s -~. at%) as is confirmed in cases where reliable D values are available.These findings are in contrast to the current published theories on eutectic solidification. Suggestions are given where the boundary conditions have to be altered in order to attain full accord between experiment and theory.

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Kurz¹,

Sahm²

1975

Gerichtet Erstarrte Eutektische Werkstoffe

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Morphologie de l'eutectique orienté CoCoAl et influence d'une addition de nickel

Cited by 11 publications

References 11 publications

Investigation of an as-sprayed NiCoCrAlY overlay coating - microstructure and evolution of the coating

Investigation of an as-sprayed NiCoCrAlY overlay coating - microstructure and evolution of the coating

Predictability of Eutectic Microstructures

Phasendiagramme

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