Keyhole threshold and morphology in laser melting revealed by ultrahigh-speed x-ray imaging

Science ◽  
2019 ◽  
Vol 363 (6429) ◽  
pp. 849-852 ◽  
Author(s):  
Ross Cunningham ◽  
Cang Zhao ◽  
Niranjan Parab ◽  
Christopher Kantzos ◽  
Joseph Pauza ◽  
...  
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
High Energy ◽  
X Rays ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Powder Bed ◽  
Three Dimensional Printing ◽  
X Ray ◽  
X Ray Imaging

We used ultrahigh-speed synchrotron x-ray imaging to quantify the phenomenon of vapor depressions (also known as keyholes) during laser melting of metals as practiced in additive manufacturing. Although expected from welding and inferred from postmortem cross sections of fusion zones, the direct visualization of the keyhole morphology and dynamics with high-energy x-rays shows that (i) keyholes are present across the range of power and scanning velocity used in laser powder bed fusion; (ii) there is a well-defined threshold from conduction mode to keyhole based on laser power density; and (iii) the transition follows the sequence of vaporization, depression of the liquid surface, instability, and then deep keyhole formation. These and other aspects provide a physical basis for three-dimensional printing in laser powder bed machines.

scholarly journals Measurement of Carbon Ion Photoabsorption Cross Sections Using Laser Plasmas

1990 ◽  
Vol 115 ◽  
pp. 53-56
Author(s):  
B. Wargelin ◽  
S.M. Kahn ◽  
W. Craig ◽  
R. London
Keyword(s):  
Cross Sections ◽  
Grazing Incidence ◽  
X Rays ◽  
Carbon Ion ◽  
X Ray ◽  
Laser Plasmas ◽  
X Ray Imaging ◽  
Low Temperature Plasmas ◽  
Ion Species ◽  
High Column

AbstractLaser plasmas are well-suited to studies of ionic photoabsorption because they can provide highly ionized, low temperature plasmas of high column density, as well as bright, compact continuum X-ray sources which can illuminate the plasma under study. In our experiment, continuum X-rays from a gold laser plasma are partially absorbed as they traverse a carbon plasma and are then dispersed by a grazing incidence reflection grating. An X-ray imaging camera records both the absorbed and unabsorbed spectra simultaneously for later computer analysis to determine the photoabsorption cross sections for each carbon ion species.

scholarly journals Tomosaic: efficient acquisition and reconstruction of teravoxel tomography data using limited-size synchrotron X-ray beams

2018 ◽  
Vol 25 (5) ◽  
pp. 1478-1489 ◽  
Author(s):  
Rafael Vescovi ◽  
Ming Du ◽  
Vincent de Andrade ◽  
William Scullin ◽  
Dogˇa Gürsoy ◽  
...  
Keyword(s):  
Imaging System ◽  
Three Dimensional ◽  
Computing System ◽  
X Rays ◽  
X Ray ◽  
High Penetration ◽  
X Ray Imaging ◽  
Software Modules ◽  
Dimensional Reconstruction ◽  
Tomography Data

X-rays offer high penetration with the potential for tomography of centimetre-sized specimens, but synchrotron beamlines often provide illumination that is only millimetres wide. Here an approach is demonstrated termed Tomosaic for tomographic imaging of large samples that extend beyond the illumination field of view of an X-ray imaging system. This includes software modules for image stitching and calibration, while making use of existing modules available in other packages for alignment and reconstruction. The approach is compatible with conventional beamline hardware, while providing a dose-efficient method of data acquisition. By using parallelization on a distributed computing system, it provides a solution for handling teravoxel-sized or larger datasets that cannot be processed on a single workstation in a reasonable time. Using experimental data, the package is shown to provide good quality three-dimensional reconstruction for centimetre-sized samples with sub-micrometre pixel size.

Three-Dimensional X-Ray Diffraction Microscopy Using High-Energy X-Rays

MRS Bulletin ◽  
2004 ◽  
Vol 29 (3) ◽  
pp. 166-169 ◽  
Author(s):  
Henning F. Poulsen ◽  
Dorte Juul Jensen ◽  
Gavin B.M. Vaughan
Keyword(s):  
Materials Science ◽  
Three Dimensional ◽  
High Energy ◽  
Polycrystalline Materials ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reconstruction Methods ◽  
The Individual ◽  
Individual Grains

AbstractThree-dimensional x-ray diffraction (3DXRD) microscopy is a tool for fast and nondestructive characterization of the individual grains, subgrains, and domains inside bulk materials. The method is based on diffraction with very penetrating hard x-rays (E ≥ 50 keV), enabling 3D studies of millimeter-to-centimeter-thick specimens.The position, volume, orientation, and elastic and plastic strain can be derived for hundreds of grains simultaneously. Furthermore, by applying novel reconstruction methods, 3D maps of the grain boundaries can be generated. The 3DXRD microscope in use at the European Synchrotron Radiation Facility in Grenoble, France, has a spatial resolution of ∼5 μm and can detect grains as small as 150 nm. The technique enables, for the first time, dynamic studies of the individual grains within polycrystalline materials. In this article, some fundamental materials science applications of 3DXRD are reviewed: studies of nucleation and growth kinetics during recrystallization, recovery, and phase transformations, as well as studies of polycrystal deformation.

scholarly journals Data assimilation of structural deformation using finite element simulations and single-perspective projection data based on the example of X-ray imaging

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Ines Butz ◽  
Stefan Moser ◽  
Siegfried Nau ◽  
Stefan Hiermaier
Keyword(s):  
Finite Element ◽  
Data Assimilation ◽  
High Speed ◽  
Three Dimensional ◽  
High Energy ◽  
Video Data ◽  
Two Dimensional ◽  
Complex Deformation ◽  
X Ray ◽  
X Ray Imaging

AbstractGaining insight in the complex deformation processes inside a vehicle during the process of crashing is to date only possible via numerical simulations. To validate these simulations experimentally, high speed, high-energy X-ray imaging is currently developed. So far, X-ray images have only been compared qualitatively to simulations as quantitative analysis proves challenging: Three dimensional (3D) information has to be reconstructed from two dimensional (2D) X-ray images showing overlapping parts which undergo complex deformation. We propose a novel analysis method which adapts ideas from data assimilation to reconstruct three dimensional motion and deformation from two dimensional measurements using high speed X-ray video data and finite element (FE) simulations. Furthermore, we analyze the accuracy of the approach based on an observing system simulation experiment.

Measurements of Electron Impact K-shell Ionization Cross Sections of Cr21+ Ions

2021 ◽  
Author(s):  
David Vogel ◽  
Peter Beiersdorfer ◽  
Keith Wong ◽  
Ron Zasadzinski ◽  
Ming Feng Gu
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
X Rays ◽  
Distorted Wave ◽  
Ionization Cross ◽  
X Ray ◽  
Relative Cross Section ◽  
Inner Shell Ionization ◽  
Ionization Cross Sections ◽  
Shell Ionization

We present relative cross section measurements of the inner-shell ionization of highly charged chromium ions by high-energy (7-30 keV) electrons. The measurements use a technique based on high-resolution x-ray spectroscopy, which correlates ionization events with K∝ decay x rays. Moreover, the measurements show that inner-shell ionization only affects the strength of the heliumlike 1s2s 3S1 -> 1s2 1S0 forbidden line. The cross sections inferred for Li-like Cr21+ agree well with distorted wave calculations.

scholarly journals All-inorganic Perovskite Nanocrystals: New Generation Scintillators for High-Resolution X-Ray Imaging

2022 ◽  
Author(s):  
Lu Lu ◽  
Mingzi Sun ◽  
Tong Wu ◽  
Qiuyang Lu ◽  
Baian Chen ◽  
...  
Keyword(s):  
High Resolution ◽  
Visible Light ◽  
High Energy ◽  
X Rays ◽  
Inorganic Perovskite ◽  
Perovskite Nanocrystals ◽  
X Ray ◽  
X Ray Imaging ◽  
New Generation

With super strong penetrability, high-energy X-rays can be applied to probe the inner structure of target objects under nondestructive situations. Scintillation materials can down-convert X-rays into visible light, enabling the...

Metal Microstructures in Four Dimensions

2004 ◽  
Author(s):  
S. F. Nielsen ◽  
C. Gundlach ◽  
E. M. Lauridsen ◽  
R. V. Martins ◽  
H. F. Poulsen ◽  
...  
Keyword(s):  
Grain Growth ◽  
Three Dimensional ◽  
High Energy ◽  
Third Generation ◽  
Plastic Strains ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Four Dimensions

By Three Dimensional X-ray Diffraction (3DXRD) microscopy it is possible to characterize microstructures non-destructively in 3 dimensions. The measurements are furthermore typically so fast that dynamics may be monitored in-situ, giving also the 4th dimension, namely the time. The 3DXRD technique is based on diffraction of high energy x-rays from third generation synchrotron sources. In the present paper the 3DXRD technique is described and it’s potentials are illustrated by examples relating to elastic and plastic strains, recovery, recrystallization and grain growth.

Defects of Platelet Function Recognized by X-Ray Imaging and Scanning Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 610-613
Author(s):  
M.G. Baldini ◽  
S. Morinaga ◽  
D. Minasian ◽  
R. Feder ◽  
D. Sayre ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Biology ◽  
Imaging Technique ◽  
Human Platelets ◽  
X Rays ◽  
X Ray ◽  
X Ray Imaging ◽  
Complex Phenomena ◽  
Scanning Electron

Contact X-ray imaging is presently developing as an important imaging technique in cell biology. Our recent studies on human platelets have demonstrated that the cytoskeleton of these cells contains photondense structures which can preferentially be imaged by soft X-ray imaging. Our present research has dealt with platelet activation, i.e., the complex phenomena which precede platelet appregation and are associated with profound changes in platelet cytoskeleton. Human platelets suspended in plasma were used. Whole cell mounts were fixed and dehydrated, then exposed to a stationary source of soft X-rays as previously described. Developed replicas and respective grids were studied by scanning electron microscopy (SEM).

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