Differentiation of γ′- and γ″- precipitates in Inconel 718 by a complementary study with small-angle neutron scattering and analytical microscopy

Lawitzki, Robert; Hassan, Sameeha E; Karge, Lukas; Wagner, Julia; Wang, D.; Kobylinski, Jonas von; Krempaszky, Christian; Hofmann, M.; Gilles, Ralph; Schmitz, Guido

doi:10.1016/j.actamat.2018.10.014

Cited by 88 publications

(17 citation statements)

References 39 publications

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“…The c¢¢ phase is often represented stoichiometrically as Ni 3 Nb. Lawitzki et al [34] has measured the elemental composition of the c¢¢ phase in IN718 samples with similar element composition to our samples using atom probe tomography, showing that the c¢¢ consists of 71.1 pct of Ni, 17.5 pct of Nb, 1 pct of Al, 4.3 pct of Ti, 2.4 pct of Cr, 1.8 pct of Fe, and 1.9 pct of Mo in at. pct.…”

Section: Change In Compositionsupporting

confidence: 73%

Evolution of Lattice Spacing of Gamma Double Prime Precipitates During Aging of Polycrystalline Ni-Base Superalloys: An In Situ Investigation

Zhang

Qin

et al. 2019

Metall Mater Trans A

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Inconel 718 derives the strengthening mainly from Ni 3 Nb c¢¢ phase. To investigate the evolution of lattice spacing of c¢¢ precipitates, in situ neutron diffraction experiments were performed during aging heat treatment of two Inconel 718 bar samples at 780°C for 8 hours. One sample was aged with a negligible applied stress (5 MPa) and the other with an applied tensile stress of 300 MPa. The diffraction data demonstrate three stages of lattice spacing evolution due to compositional and morphological changes during aging. (1) Stage I, the c lattice spacing decreases isotropically in the first hour of aging as the composition changes. (2) Stage II, the c lattice spacing decreases and the c¢¢ lattice spacing increases between 1 and 5 hours of aging, at this stage compositional change on the lattice evolution weakens with aging time and the morphological change becomes comparable. (3) Stage III, as aging proceeds, compositional change is negligible, while morphological change is dominant; the c lattice spacing decreases in the longitudinal direction but increases in the transverse direction; in contrast, the converse occurs in c¢¢ lattice spacing evolution.

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Section: Change In Compositionsupporting

confidence: 73%

Evolution of Lattice Spacing of Gamma Double Prime Precipitates During Aging of Polycrystalline Ni-Base Superalloys: An In Situ Investigation

Zhang

Qin

et al. 2019

Metall Mater Trans A

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“…The alloy composition in our study is similar to that used in their study, in addition, they reported chemical compositions of c¢¢ phase were similar after different aging heat treatments. [25] Thereby, we assumed the compositions of c and c¢¢ phases in our study were similar to those in reference and adopted these scattering length densities to the estimation of c¢¢ volume fraction in the current study. The diffracted neutron beam wavelength is proportional to the d-spacing when the diffraction angle is fixed according to the Bragg's law:…”

Section: E Volume Fraction Of C¢¢mentioning

confidence: 99%

“…The size of the c¢¢ particle is typically less than 100 nm in diameter and less than 20 nm in thickness after the aging heat treatment, while the volume fraction of c¢¢ phase is less than 15 pct as reported in literature. [17][18][19][20][21][22][23][24][25] In order to utilize the in-situ neutron diffraction technique related to the c¢¢ phase in Ni-base superalloys, an accurate fitting to the c¢¢ peaks is necessary. Therefore, an approach to obtain c¢¢ diffraction peaks with satisfying quality is required.…”

Section: In-situ Neutron/synchrotron Diffraction Techniquesmentioning

confidence: 99%

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Using Variant Selection to Facilitate Accurate Fitting of γ″ Peaks in Neutron Diffraction

Zhang

Qin

et al. 2019

Metall Mater Trans A

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c¢¢ diffraction peaks are hard to discern in neutron/X-ray diffraction patterns, hindering studies on the c¢¢-strengthened superalloys using in-situ diffraction. In this study, we propose a variant selection method to increase the intensity of c¢¢ peaks and to facilitate accurate fitting. The specific variants of c¢¢ are controlled by applying a 300 MPa tensile stress during aging at 790°C for 5 hours. The interaction energy between the applied stress and the transformation strain of each c¢¢ variant differs, leading to an increase in the amount of the variants with a greater energy reduction at the expense of other variants. The enhanced variants result in greater c¢¢ peak intensities in neutron diffraction patterns, allowing both the Pawley refinement and single peak fitting to be performed. Lattice parameters of c¢¢ and c phases, and lattice misfit between the two phases and volume fraction of c¢¢ are acquired. The uncertainties associated with the fitting maintain an acceptable level corresponding to 150 microstrains. The proposed variant selection method shows potential for studying the role of c¢¢ phase in Ni-base superalloys.

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“…The transmission electron microscopy (TEM) [5,7] and atom probe tomography (APT) [8] measurements similarly give a range of about 10∼15 %. However, the latest quantification by small-angle neutron scattering (SANS) [9] and neutron diffraction [10] suggest lower volume fractions of γ ′′ : 3.8 % and 7.9 %, respectively.…”

Section: Inconel 718mentioning

confidence: 99%

On the Microstructures and Anisotropic Mechanical Behaviours of Additively Manufactured IN718

Deng

2019

Linköping Studies in Science and Technology. Dissertations

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Additive manufacturing (AM), also known as 3D printing, offers great design flexibility for manufacturing components with complex geometries, and has attracted significant interest in the aero and energy industries in the past decades. Among the commercial AM processes, selective laser melting (SLM) and electron beam melting (EBM) are the two most widely used ones for metallic materials. Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties, weldability and low cost. Due to its excellent weldability, IN718 has been intensively applied in the AM filed, to gain more understanding of the AM processes and fully realize AM's potentials. The study objects in the present thesis include both EBM and SLM IN718. The solidification conditions in EBM and SLM are very different and are different to that of conventional cast, leading to unique microstructures mechanical properties. Therefore, this thesis aims to gain better understanding of the microstructures and anisotropic mechanical behaviours of both EBM and SLM IN718, by detailed characterizations and by comparisons with the forged counterpart. The as-built microstructure of EBM IN718 is spatially dependent: the periphery (contour) region has a mixture of equiaxed and columnar grains, while the bulk (hatch) region has columnar grains elongated along the building direction; the last solidified region close to the top sample surface shows segregation and Laves phases, otherwise the rest of the whole sample is well homogenized. Differently, the as-built microstructure of SLM IN718 is spatially homogeneous: the grains is rather equiaxed and with subgrain cell structures. These microstructures also respond differently to the standard heat treatment routines for the conventional counterparts. Anisotropic mechanical properties are evident in the room temperature tensile tests and high temperature dwell-fatigue tests. The anisotropic tensile properties of EBM IN718 at room temperature are more likely due to the directional alignment of porosities along the building direction rather than the strong crys-In these papers I have been the main contributor, performing all the experimental work, characterization, analysis and manuscript writing, under the supervision of Johan Moverare and Ru Lin Peng.

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Differentiation of γ′- and γ″- precipitates in Inconel 718 by a complementary study with small-angle neutron scattering and analytical microscopy

Cited by 88 publications

References 39 publications

Evolution of Lattice Spacing of Gamma Double Prime Precipitates During Aging of Polycrystalline Ni-Base Superalloys: An In Situ Investigation

Evolution of Lattice Spacing of Gamma Double Prime Precipitates During Aging of Polycrystalline Ni-Base Superalloys: An In Situ Investigation

Using Variant Selection to Facilitate Accurate Fitting of γ″ Peaks in Neutron Diffraction

On the Microstructures and Anisotropic Mechanical Behaviours of Additively Manufactured IN718

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