Boundary characterization using 3D mapping of geometrically necessary dislocations in AM Ta microstructure

Witzen, Wyatt A.; Polonsky, Andrew; Rottmann, Paul F.; Pusch, Kira; Echlin, McLean P.; Pollock, Tresa M.; Beyerlein, Irene J.

doi:10.1007/s10853-022-07074-2

Cited by 10 publications

(2 citation statements)

References 76 publications

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“…As a result, the cell walls can trap dislocations and serve as a scaffold to form 'as-printed dislocation cells' [5,6]. Similar as-printed dislocation structures are also observed in AM metals [7,8] and alloys without chemical cells [9]. These as-printed dislocation cells and structures hinder dislocation glide during plastic deformation, thereby affecting the mechanical properties of AM metallic materials [9,10].…”

Section: Introductionmentioning

confidence: 76%

Modeling of microscale internal stresses in additively manufactured stainless steel

Zhang

Ding

et al. 2022

Modelling Simul. Mater. Sci. Eng.

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Additively manufactured (AM) metallic materials often comprise as-printed dislocation cells inside grains. These dislocation cells can give rise to substantial microscale internal stresses in both initial undeformed and plastically deformed samples, thereby affecting the mechanical properties of AM metallic materials. Here we develop models of microscale internal stresses in AM stainless steel by focusing on their back stress components. Three sources of microscale back stresses are considered, including the printing and deformation-induced back stresses associated with as-printed dislocation cells as well as the deformation-induced back stresses associated with grain boundaries. We use a three-dimensional discrete dislocation dynamics model to demonstrate the manifestation of printing-induced back stresses. We adopt a dislocation pile-up model to evaluate the deformation-induced back stresses associated with as-printed dislocation cells. The extracted back stress relation from the pile-up model is incorporated into a crystal plasticity model that accounts for the other two sources of back stresses as well. The crystal plasticity finite element simulation results agree with the experimentally measured tension-compression asymmetry and macroscopic back stress, the latter of which represents the effective resultant of microscale back stresses of different origins. Our results provide an in-depth understanding of the origins and evolution of microscale internal stresses in AM metallic materials.

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Section: Introductionmentioning

confidence: 76%

Modeling of microscale internal stresses in additively manufactured stainless steel

Zhang

Ding

et al. 2022

Modelling Simul. Mater. Sci. Eng.

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“…As the demand for greater volume and more detailed resolution material information grows, so too does the demand and expense of EBSD mapping. Spatial resolution in EBSD is of particular interest in the characterization of deformed materials and additive manufacturing 13 , where subgrain misorientation gradients are used to quantify local plastic deformation effects and geometrically necessary dislocation densities [14][15][16] . In efforts to improve EBSD resolution and quality, simulations and experimental studies [17][18][19][20][21] have shown that lowering the electron beam accelerating voltage can significantly improve the spatial resolution of EBSD maps, but map quality and achievable resolution vary with differing materials and imaging conditions.…”

Section: Introductionmentioning

confidence: 99%

Adaptable physics-based super-resolution for electron backscatter diffraction maps

et al. 2022

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In computer vision, single-image super-resolution (SISR) has been extensively explored using convolutional neural networks (CNNs) on optical images, but images outside this domain, such as those from scientific experiments, are not well investigated. Experimental data is often gathered using non-optical methods, which alters the metrics for image quality. One such example is electron backscatter diffraction (EBSD), a materials characterization technique that maps crystal arrangement in solid materials, which provides insight into processing, structure, and property relationships. We present a broadly adaptable approach for applying state-of-art SISR networks to generate super-resolved EBSD orientation maps. This approach includes quaternion-based orientation recognition, loss functions that consider rotational effects and crystallographic symmetry, and an inference pipeline to convert network output into established visualization formats for EBSD maps. The ability to generate physically accurate, high-resolution EBSD maps with super-resolution enables high-throughput characterization and broadens the capture capabilities for three-dimensional experimental EBSD datasets.

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Microstructure and Elevated Temperature Flexure Testing of Tungsten Produced by Electron Beam Additive Manufacturing

Zhang,

Carriere,

Amoako

et al. 2023

JOM

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Due to their superior high-temperature thermomechanical capabilities, sputter erosion durability, and excellent resistance to hydrogen isotopes, tungsten materials have garnered significant interest in fusion nuclear applications. However, low room-temperature ductility and complex machining strategies present significant challenges for traditional fabrication. Electron beam powder bed fusion (EB-PBF) shows promise in manufacturing pure tungsten via high thermal energy input, elevated build temperature, and a tightly controlled high-vacuum environment. This work explores the process, structure, and property relationship of pure tungsten fabricated by EB-PBF, where 99.8% relative density was achieved with reduced cracking by isolating the build substrate and optimizing the print parameter suite. Optical and electron imaging revealed that the microstructure contained equiaxed grains along the build direction, with subgrains present in all inspected grains. Flexural testing at ambient and elevated temperatures demonstrated high ductility at 900°C and flexural strength of 470 MPa at room temperature of additively manufactured tungsten.

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Boundary characterization using 3D mapping of geometrically necessary dislocations in AM Ta microstructure

Cited by 10 publications

References 76 publications

Modeling of microscale internal stresses in additively manufactured stainless steel

Modeling of microscale internal stresses in additively manufactured stainless steel

Adaptable physics-based super-resolution for electron backscatter diffraction maps

Microstructure and Elevated Temperature Flexure Testing of Tungsten Produced by Electron Beam Additive Manufacturing

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