On diffusion in the β-NiAl phase

Paul, Aloke; Kodentsov, AA Alexander; Loo, van Fjj Frans

doi:10.1016/j.jallcom.2005.04.194

Cited by 101 publications

(79 citation statements)

References 20 publications

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“…The molar volume of the β phase is found to be 7.04×10 -6 m 3 /mol, which agrees well with the range 7.0×10 -6 ~ 7.8×10 -6 m 3 /mol for β-NiAl alloy proposed by Paul et al [64].…”

Section: β-Phase Coarsening Kineticssupporting

confidence: 89%

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Chen

McCartney

2017

Journal of Alloys and Compounds

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This paper investigates the β-phase coarsening behaviour during isothermal heat treatment of free-standing CoNiCrAlY (Co-31.7%Ni-20.8%Cr-8.1%Al-0.5%Y, all in wt%) coatings prepared by high velocity oxy-fuel (HVOF) thermal spraying. The microstructure of the coatings was characterised using scanning electron microscopy with energy dispersive X-ray (EDX) analysis and electron backscatter diffraction (EBSD). It comprises a two phase structure of fcc γ-Ni matrix and bcc β-NiAl precipitates. The volume fraction of the γ-Ni and the β-NiAl phases were measured to be around 70% and 30% respectively, with grain sizes varying largely from 0.5 to 2 µm for both phases. Isothermal heat treatments of the freestanding coatings were carried out at 1100 C for times up to 250 h. The β-phase coarsening behaviour during isothermal heat treatments was analysed by quantitative metallography. It is shown that the coarsening behaviour of β phase in the CoNiCrAlY alloy followed the classical Lifshitz-Slyozov-Wagner (LSW) theory of Ostwald ripening. By incorporating a dimensionless factor which correlates with volume fraction of the β phase, a modified LSW model coupled with formulaic interfacial energy and effective diffusion coefficient of the 2 CoNiCrAlY alloy was utilised to interpret the coarsening behaviour of the β phase. The coarsening rate coefficient obtained from the modified LSW model shows good agreement with the corresponding experimental result.

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“…The molar volume of the β phase is found to be 7.04×10 -6 m 3 /mol, which agrees well with the range 7.0×10 -6 ~ 7.8×10 -6 m 3 /mol for β-NiAl alloy proposed by Paul et al [64].…”

Section: β-Phase Coarsening Kineticssupporting

confidence: 89%

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Chen

McCartney

2017

Journal of Alloys and Compounds

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“…[26,32] Data estimated in the Ni-Al system is found to be comparable to the data estimated by conventional method using radio-isotope. [15,33] The integrated and tracer diffusion coefficients are related bỹ…”

Section: Estimation Of the Diffusion Parametersmentioning

confidence: 99%

Interdiffusion in the Ni-Zr System

Paul

2015

J. Phase Equilib. Diffus.

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Interdiffusion study is conducted in the Ni-Zr system in the temperature range of 750-850°C. Five intermetallic compounds, Ni 5 Zr, Ni 7 Zr 2 , Ni 10 Zr 7 , NiZr and NiZr 2 are found to grow in the interdiffusion zone. Integrated diffusion coefficients are estimated for different phases. Activation energy is found to be lowest for Ni 10 Zr 7 (178 ± 8 kJ/mol) and highest for NiZr (323 ± 6 kJ/mol). Tracer diffusion coefficients are estimated at the location of the Kirkendall marker plane in the Ni 7 Zr 2 phase. Ni is found to have 10 times higher diffusion rate compared to Zr in this phase. Higher diffusion rate of Ni compared to Zr is found, which is expected because of higher number of Ni-Ni bonds compared to Zr-Zr bonds in this phase.

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“…6 shows, the growth rate of the outwardgrowing layer drastically increased after the lining layer had become almost single phase of Al 3 Ni 2 , and it decreased after the microchannel had completed at about 1273 K. It is well known that the diffusion rate of aluminum is higher than nickel in the Al-rich Al-Ni intermetallic compounds i.e., Al 3 Ni, Al 3 Ni 2 , NiAl Al . [30][31][32] Especially in Al 3 Ni and Al 3 Ni 2 , aluminum atoms dominate the diffusion process. 31) In addition, the fact that Al 3 Ni 2 is the dominant reaction phase between Al and Ni in its thermodynamically stable temperature range indicates that the diffusion rate in Al 3 Ni 2 is higher than any of the other Al-Ni intermetallic compounds.…”

Section: Structure Evolution Around the Microchannelmentioning

confidence: 99%

Formation of Al-Ni Intermetallic Layers Lining Microchannels Produced by Powder-Metallurgical Process Using Aluminum Sacrificial Cores

Ohmi

Hayashi

2016

Mater. Trans.

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The mechanism of in-situ formation of Al-Ni intermetallic lining layers during microchannel formation in nickel bodies by a powder-metallurgical process has been investigated. Aluminum wire was used as a sacri cial core that gives the shape of the microchannel and supplies the alloying element for the lining layer. Nickel powder compacts with 29(±1)% porosity containing aluminum wires were heated from room temperature and then quenched at various temperatures between 873 K and 1473 K. Porous intermetallic lining layers were clearly recognized at temperatures above 1073 K. Each lining layer was built up from an outward-growing layer and an inward-growing layer. Change in the voidage in the outward-growing layer during heat treatment and the formation of a high-voidage zone around the lining layer were accounted for in terms of phase equilibria and unequal diffusion rates of the alloy elements in the Al-Ni intermetallic compounds and nickel solid solution.

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On diffusion in the β-NiAl phase

Cited by 101 publications

References 20 publications

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Interdiffusion in the Ni-Zr System

Formation of Al-Ni Intermetallic Layers Lining Microchannels Produced by Powder-Metallurgical Process Using Aluminum Sacrificial Cores

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