Interdiffusion and intrinsic diffusion in the Ni AI (δ) phase of the Al-Ni system

Shankar, Sumanth; Seigle, L.

doi:10.1007/bf02661819

Cited by 259 publications

(105 citation statements)

References 16 publications

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“…It is also higher than Q* Ni as well as the values of the activation energies for interdiffusion in stoichiometric NiAl, which have been measured to be about 195 kJ mol -1 [32] and about 355 kJ mol -1 [33]. where once again Q c and σ are in kJ mol -1 and MPa, respectively.…”

Section: Temperature Dependence Of the Secondary Creep Ratementioning

confidence: 75%

“…Details of these diffusion mechanisms are discussed elsewhere [31,55,56]. An examination of Table 5 shows that the four-ring (4R) mechanism predicts very high activation energies for diffusion, which is not observed in both diffusion [30,31,32,33,34] as well as in creep experiments. Therefore, Mishin and Farkas [55] concluded that this mechanism is unimportant in diffusion in NiAl.…”

Section: Comparison Of the Activation Energy For Creep In Regime II Wmentioning

confidence: 99%

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Tensile creep of polycrystalline near-stoichiometric NiAl

Raj

2003

Materials Science and Engineering: A

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Long term tensile creep studies were conducted on binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms.Inverse and normal primary creep curves were observed depending on stress and temperature. It is concluded that the primary creep of NiAl is limited by dislocation mobility. The stress exponent for creep, n, decreased from 13.9 at 700 K to 5.5 at 1200 K. The true activation energy

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Section: Temperature Dependence Of the Secondary Creep Ratementioning

confidence: 75%

Section: Comparison Of the Activation Energy For Creep In Regime II Wmentioning

confidence: 99%

Tensile creep of polycrystalline near-stoichiometric NiAl

Raj

2003

Materials Science and Engineering: A

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“…In addition, in the NiAl intermetallic phase, the diffusivity of Ni is higher than that of Al on the Ni-rich side. 21) In the aluminized coating close to the IDZ, the NiAl phase was Ni-rich, confirming that the outward diffusion of Ni was greater than the inward diffusion of Al. This mechanism seems to be another factor causing void growth.…”

Section: ¹1mentioning

confidence: 78%

Effect of Thermal History on Microstructural Changes in Aluminized Nickel-Based Single-Crystal Superalloy

2013

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The effect of the thermal history on microstructural changes in aluminized and Pt-aluminized Ni-based single-crystal superalloys was investigated. The superalloy substrates were first electropolished to get rid of the residual surface strain. Then, Pt was electrodeposited and vacuum annealing was conducted for some of the substrates, and aluminized and Pt-aluminized specimens were prepared using the conventional aluminizing process. It was found that in the aluminized specimens, voids were formed in the vicinity of the substrate/coating interfaces during thermal cyclic heating, whereas secondary diffusion zones (SDZ) were formed by isothermal heating. These different microstructural changes of the aluminized specimens can be explained by the kinetics of diffusion between the coating layer and the substrate during the heating/cooling processes. In the Pt-aluminized specimen, on the other hand, secondary reaction zone (SRZ) formation was observed after both thermal cyclic and isothermal treatments. These results can be explained by the polycrystallization of the substrate surface during the annealing process, which promotes interdiffusion, resulting in the formation of an SRZ.

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“…In the case of the NiAl intermetallic phase, diffusivity of Ni is higher than that of Al on the Ni-rich side, and vice versa. 13) In the aluminized coating layer close to IDZ, the composition of NiAl became Ni-rich and thus the outward diffusion of Ni is dominant rather than the inward diffusion Al. In addition, when the specimen was heated, the compressive stress was applied to the substrate and the tensile stress being applied to the coating layer, resulting in the accelerated outward diffusion of elements.…”

Section: Discussionmentioning

confidence: 99%

Effect of Surface Treatment and Crystal Orientation on Microstructural Changes in Aluminized Ni-Based Single-Crystal Superalloy

et al. 2011

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The effect of pre-surface treatment and crystal orientation on microstructural changes in the aluminized 4th generation Ni-based singlecrystal superalloy TMS-138 was investigated. The substrate superalloy was cut along the {100} and {110} planes on which three kinds of surface finishing, such as grit blasting, mechanical polishing and electro-polishing were conducted prior to the conventional high-activity aluminizing process. A thermal cycling test at 1373 K revealed that heavy deformation of the substrate surface by grit blasting gave rise to the formation of a secondary reaction zone (SRZ) in the vicinity of the interdiffusion zone/substrate interfaces. When the surfaces were finished by electropolishing, voids were formed in the vicinity of the interdiffusion zone/substrate interfaces. It was also found that accelerated formation of SRZ and voids was observed along the h110i directions rather than the h100i directions during the thermal cycling test. The difference in morphological changes of substrates can be related to the residual stress introduced by the surface finishing.

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Interdiffusion and intrinsic diffusion in the Ni AI (δ) phase of the Al-Ni system

Cited by 259 publications

References 16 publications

Tensile creep of polycrystalline near-stoichiometric NiAl

Tensile creep of polycrystalline near-stoichiometric NiAl

Effect of Thermal History on Microstructural Changes in Aluminized Nickel-Based Single-Crystal Superalloy

Effect of Surface Treatment and Crystal Orientation on Microstructural Changes in Aluminized Ni-Based Single-Crystal Superalloy

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