Nano <i>γ′/γ</i>″ composite precipitates in Alloy 718

Phillips, Peter; McAllister, Donald; Gao, Yipeng; Lv, Duchao; Williams, Robert E.A.; Peterson, Benjamin; Wang, Y.; Mills, Michael J.

doi:10.1063/1.4721456

Cited by 35 publications

(19 citation statements)

References 12 publications

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“…8a, were observed. In the present research, the compact morphology, in which the cuboidal γ′ particles are coated on all six faces with a shell of γ″ precipitates [3], or the composite γ′-γ″ morphology (coffee-bean-shaped co-precipitates, γ″ was in contact with γ′) [20][21][22] has not been observed. The ratio of the combined atomic contents of Al and Ti to the atomic content of Nb, (Al+Ti)/Nb, is a measure of the compact morphology proposed by Cozar and Pineau [3].…”

Section: Discussionmentioning

confidence: 89%

Investigations of γ′, γ″ and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting

Cao

Sun

Wang

et al. 2018

Materials Characterization

175

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Inconel 718 alloy samples were fabricated by selective laser melting (SLM). Microstructure and precipitation in solution-heat-treated-and double-aging-SLM-made Inconel 718 were studied by scanning and transmission electron microscopy. Electron microscope observations showed that disc-shaped and cuboidal γ″, and circular γ′ precipitates with an average size of 10-50 nm developed within cellular γ austenite matrix. The simulated, experimentally observed electron diffraction patterns, and dark-field imaging further revealed that the precipitation of three variants of γ″ in the γ matrix occurred. The coarser acicular γ″, and globular as well as plate-like δ phases precipitated at grain boundaries and also within the interior of austenite matrix. The morphology, distribution and crystallography of these precipitates and their formation mechanisms were analyzed and discussed. Investigations of γ′, γ ″and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting." Materials Characterization 136 (2018): 398-406. AbstractInconel 718 alloy samples were fabricated by selective laser melting (SLM).Microstructure and precipitation in solution-heat-treated-and double-aging-SLM-made Inconel 718 were studied by scanning and transmission electron microscopy. Electron microscope observations showed that disc-shaped and cuboidal γ″, and circular γ′ precipitates with an average size of 10 -30 nm developed within cellular γ austenite matrix. The simulated, experimentally observed electron diffraction patterns, and dark-field imaging further revealed that the precipitation of three variants of γ″ in the γ matrix occurred. The coarser needle-like γ″, and globular as well as plate-like δ phases precipitated at grain boundaries and also within the

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Section: Discussionmentioning

confidence: 89%

Investigations of γ′, γ″ and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting

Cao

Sun

Wang

et al. 2018

Materials Characterization

175

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“…This difference provides strong evidence that the process-structure-property relationships for L-PBF AM-IN718 materials likely differ than for the DED material. Furthermore, several microstructure features known to be important to attain the best performances from traditionally manufactured IN718 are yet to be studied in AM-IN718, such as g¢/g″ coprecipitation [23]. Complete knowledge of the interactions of all of the microstructure features of AM-IN718 is necessary to develop and qualify better heat treatments for AM-IN718 materials with confidence and purpose.…”

Section: Motivationmentioning

confidence: 99%

“…The g¢ unit cell size is in between that of the g matrix and g″ precipitates. Therefore, it is proposed that g¢ -matrix interfaces serve as preferential nucleation sites for g″ [28], because the lattice strain energy caused by g″ nucleating on g¢ -matrix interfaces is lower than that of g″ nucleating completely within the matrix [23,32,33]. Coprecipitates have been shown to improve mechanical responses by requiring more complex dislocation structures to induce plastic deformation [34,35].…”

Section: Structure-property Relationshipsmentioning

confidence: 99%

“…However, note that the top side of the g¢ and g″ interface is rounded and not atomically planar, while the bottom interface of the g″ phase is atomically planar. It is known that one of the three coherent, coprecipitate variants of the g¢ and g″ phases has an atomically planar [001]g″ interface that can be viewed edge-on in this <110>g viewing direction [23]. Thus, the observation of this atomically-flat interface definitively indicates their presence.…”

Section: The Standard Heat Treatment Applied To Entire Build (Sht-1) mentioning

confidence: 99%

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Knowledge of process-structure-property relationships to engineer better heat treatments for laser powder bed fusion additive manufactured Inconel 718

Gallmeyer

Moorthy

Kappes

et al. 2020

Additive Manufacturing

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Dislocation structures, chemical segregation, γ′, γ″, ! precipitates and Laves phase were quantified within the microstructures of Inconel 718 (IN718) produced by laser powder bed fusion additive manufacturing (AM) and subjected to standard, direct aging, and modified multi-step heat treatments. Additionally, heat-treated samples still attached to the build plates vs. those removed were also documented for a standard heat treatment. The effects of the different resulting microstructures on room temperature strengths and elongations to failure is revealed. Knowledge derived from these process-structure-property relationships was used to engineer a super-solvus solution anneal at 1020 ºC for 15 minutes, followed by aging at 720 ºC for 24 hours heat treatment for AM-IN718 that eliminates Laves and δ phases, preserves AM-specific dislocation cells that are shown to be stabilized by MC carbide particles, and precipitates dense γ′ and γ″ nanoparticle populations. This "optimized for AM-IN718 heat treatment" results in superior properties relative to wrought/additively manufactured, then industry standard heat treated IN718: relative increases of 7/10% in yield strength, 2/7% in ultimate strength, and 23/57% in elongation to failure are realized, respectively, regardless of as-built vs. machined surface finishes.

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“…Σ9 and Σ27a show clear boron segregation on them. Gibbsian interfacial excess values show segregation to be inversely correlated with energy of CSL grain boundaries [2]. APT results for specimens containing Σ3, Σ9, and Σ27a grain boundaries.…”

mentioning

confidence: 87%

Grain Boundary Analysis of Inconel 718 Using a Novel Atom Probe Design

et al. 2018

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In this work, we present a study of correlative grain boundary segregation analysis for an Inconel 718 superalloy using a newly-designed atom probe. The EIKOS™ atom probe provides a simpler design than the CAMECA's Local Electrode Atom Probe (LEAP™) and is primarily targeted towards metallurgical applications. The specimen carrier uses a wire geometry, which is well-suited for electropolishing methods of sample preparation, but can also accommodate focused ion beam (FIB) prepared liftout specimens. In addition, the EIKOS™ atom probe also offers a novel design where the specimen and counter-electrode are integrated within the same specimen carrier. The specimen-counter electrode assembly is aligned ex-situ, allowing for no moving stage parts within the UHV analysis chamber. The specimen assembly is attached directly to a cryogenic cooler during analysis, providing high data quality without the need for complicated cryogenically cooled moving stage parts. A 532 nm green laser can also be used to assist field evaporation of poor electrical conductivity materials such as semiconductors and oxides. Data analysis is performed using CAMECA's Integrated Visualization and Analysis Software (IVAS™).For this grain boundary study, correlative techniques were used to study segregation behavior in a variety of different grain boundary types of Inconel 718. Electron backscatter diffraction (EBSD) was performed on a highly polished surface. Grain boundaries with coincident site lattice (CSL) values of Σ3, Σ9, and Σ27a were located on the sample surface from the EBSD analysis, and FIB liftout techniques were used to mount the grain boundary containing specimens to a wire-shaped substrate. Transmission EBSD was used during the sharpening process to position the grain boundary in the final needle-shaped specimen [1]. Figure 1a shows the EBSD map highlighting the Σ9 grain boundary. Figures1 b and c show the sharpening process. Figure 1d shows a transmission EBSD map highlighting the Σ9 grain boundary position within the final needle-shaped specimen.Ion distribution maps from atom probe analysis are shown in Figure 2a-c for Inconel 718 [3]. The density map in Figure 2a shows a density discontinuity at the grain boundary position because of differing field evaporation characteristics at the boundary. The density map confirms collection of the grain boundary for Σ3 boundary where no segregation was observed. Σ9 and Σ27a show clear boron segregation on them. Gibbsian interfacial excess values show segregation to be inversely correlated with energy of CSL grain boundaries [2]. References:[1] K. Babinsky, R. De Kloe, H. Clemens, S. Primig, A novel approach for site-specific atom probe specimen preparation by focused ion beam and transmission electron backscatter diffraction, Ultramicroscopy. 144 (2014) [2] P

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Nano γ′/γ″ composite precipitates in Alloy 718

Cited by 35 publications

References 12 publications

Investigations of γ′, γ″ and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting

Investigations of γ′, γ″ and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting

Knowledge of process-structure-property relationships to engineer better heat treatments for laser powder bed fusion additive manufactured Inconel 718

Grain Boundary Analysis of Inconel 718 Using a Novel Atom Probe Design

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