On the kinetics of rafting in CMSX-4 superalloy single crystals

Matan, Narumol; Cox, D. C.; Rae, C.M.F.; Reed, Roger C.

doi:10.1016/s1359-6454(99)00093-2

Cited by 225 publications

(123 citation statements)

References 27 publications

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“…For example, creep deformation occurs at a rate dependent upon diffusional rearrangements at dislocation cores [1]. Directional coarsening of the γ phase (the so-called rafting effect) requires mass transport on the scale of the periodicity of the γ precipitates [2]. Single crystal superalloys can interdiffuse with coatings applied to them [3] and oxidation occurs at a rate which is diffusion-controlled [4].…”

Section: Introductionmentioning

confidence: 99%

On the Diffusion of Alloying Elements in the Nickel-Base Superalloys

Fu¹,

Reed²,

Janotti³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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The diffusion of transition metal solutes in nickel has been studied using quantum-mechanical first principles methods, and the predictions compared critically with the experimental data available in the literature. For the 4d and 5d rows which contain Ru and Re respectively, diffusion rates are largest for elements at the far west and far east of the d-block of transition metals. The calculations reveal that this is due to a significant barrier energy for solute-vacancy exchange for elements residing at the centre of the period, e.g. Ru and Re, despite their displaying atomic sizes which are closest to that of Ni. Thus it is demonstrated conclusively that the underlying electronic bonding controls the rate of diffusion. Elements such as Ru and Re are amongst the most dense and least compressible of the transition metals due to their configuration of electrons -when alloyed with Ni this causes directional and incompressible Ni-Ru and Ni-Re bonds to be formed which hinder vacancy migration. These effects dominate over any differences in the vacancy-solute binding energy and any influence of the atomic radius of the solute. In this respect, the results disprove the traditional view that diffusion of substitutional solutes is least rapid when the size misfit with the host is the greatest. The trends for the 3d row are also studied, and it is shown that magnetism has a profound effect. Finally, if the theoretical results are to be rationalised with the experimental data, it is demonstrated that the correlation factor -which accounts for diffusional jumps in the reverse direction -should be included in the model. The results explain why some elements -for example Re -have a strong effect on the high temperature properties of the superalloys, and provide insights for future alloy design efforts.

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Section: Introductionmentioning

confidence: 99%

On the Diffusion of Alloying Elements in the Nickel-Base Superalloys

Fu¹,

Reed²,

Janotti³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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“…[16,17] The difference of the driving force for rafting with and without this relaxation is shown in Fig. 13.…”

Section: Resultsmentioning

confidence: 99%

3D-FEM Calculations of Rafting in Ni-Base Superalloys Based on High Temperature Elastic and Lattice Parameters

Osawa¹,

Shiraishi²,

Yokokawa³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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The elastic constants of and ' phases, the component phases of Ni-base superalloys, these belong to 1 st , 2 nd , and 3 rd generation, have been measured at 900 C. Three dimensional FEM calculations have been conducted based on these measured elastic constants and lattice misfit. The elastic constants have been different between generations of superalloys, depending mainly on the amount of Re. The predicted raft structure have been different among the alloys, and it also depends on the introduction of interfacial dislocations.

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“…The primary slip plane was identified using Laue X-ray imaging and the test-piece sectioned vertically, parallel to the tensile axis. For high resolution imaging the primary slip plane (-111) was perpendicular to the foil normal [110] and the Burgers vector of the highest Schmid Factor [1][2][3][4][5][6][7][8][9][10][11][12](-111) slip system lies in the plane of the foil. Hence an edge dislocation in this system a/3 [1][2][3][4][5][6][7][8][9][10][11][12] has its line vector parallel to the foil normal and would be in the ideal configuration to image the atom alignment at high resolution.…”

Section: Methodsmentioning

confidence: 99%

“…Their creep strength derives from the regular arrays of ordered L1 2 precipitates that resist the ingress of regular FCC lattice dislocations [1,2]. At high temperatures the role of the precipitates is largely to exclude dislocations, forcing them to move in the remaining 30% of γ phase by a combination of glide and climb [3]. But in the important low temperature regime, experienced in the hottest part of the engine where the high pressure turbine blades are cooled, dislocations are able to enter the γ .…”

Section: Introductionmentioning

confidence: 99%

Dislocations in a Ni-based superalloy during low temperature creep

Rae

Vorontsov

Kovařík

et al. 2014

MATEC Web of Conferences

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Abstract.The nature and variety of the dislocations passing through the two-phase γ γ microstructure of Ni-based superalloys is key to the properties of these materials. The chemistry, size and arrangement of the precipitates greatly affects the nature of these dislocations. We present High Angle Annular Dark Field (HAADF) TEM observations of the structure of dislocations entering, passing through the γ precipitates in the singlecrystal superalloy CMSX-4 R . The creep deformation of the sample was interrupted after 8 hours at 750 • C and 750 MPa, a critical stage just as secondary creep was being established, and shows a range of defects in both phases, not always those predicted by the Schmid factor for the deformation geometry. We show that dislocations lodged in the γ γ interfaces have a significant effect on the structure of the interface and that they combine to produce stacking faults which cut through the γ . The implications of these observations for secondary creep deformation are discussed.CMSX-4 R is a registered Trade Mark of the Cannon Muskegon Company.

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On the kinetics of rafting in CMSX-4 superalloy single crystals

Cited by 225 publications

References 27 publications

On the Diffusion of Alloying Elements in the Nickel-Base Superalloys

On the Diffusion of Alloying Elements in the Nickel-Base Superalloys

3D-FEM Calculations of Rafting in Ni-Base Superalloys Based on High Temperature Elastic and Lattice Parameters

Dislocations in a Ni-based superalloy during low temperature creep

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