High-resolution <i>in situ</i> characterization of laser powder bed fusion via transmission X-ray microscopy at X-ray free-electron lasers

In this work, we describe the instrumentation used to perform the first operando transmission X-ray microscopy (TXM) and simultaneous X-ray diffraction of laser melting simulating laser powder bed fusion on the XCS instrument at the Linac Coherent Light Source (LCLS) X-ray free-electron laser (XFEL). Our TXM with 40× magnification in the X-ray regime at 11 keV gave spatial resolutions down to 940 nm per line pair, with effective pixel sizes down to 206 nm, image integration times of <100 fs, and frame rates tunable between 2.1 and 119 ns for two probe frames (0.48 GHz to 8.4 MHz). Images were recorded on Zyla and Icarus (UXI) detectors to trade off between spatial resolution and time dynamics. A 1 kW CW IR laser was coupled into the interaction point to conduct pump-probe studies of laser melting and solidification dynamics. Our temporal and spatial resolution with attenuation-based contrast exceeds that currently possible with synchrotron-based high-speed radiography. This system was sensitive to feature velocities of 10-12000 m s<sup>-1</sup> but we did not observe any motion in this range in the laser melting of Al6061 alloy. Shockwaves were not observed and hot cracking proceeded at velocities below the detection limits. Pore accumulation was observed between successive shots, indicating that bubble escape mechanisms were not active. With proper experimental design, the spatial resolution, contrast and field of view could be further improved or modified. The increased brightness and narrower bandwidth of the XFEL allowed for this imaging technique and it lays the groundwork for a wide range of operando techniques to study additive manufacturing.

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Publication Details

Journal
Journal of Synchrotron Radiation
Published
2025-03-13
DOI
https://doi.org/10.1107/s1600577525001675
Primary Topic
Advanced X-ray Imaging Techniques
Type
article
Field-Weighted Citation Impact
0.00

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article

High-resolution in situ characterization of laser powder bed fusion via transmission X-ray microscopy at X-ray free-electron lasers

Matthew Seaberg, Zane Taylor, Matthieu Chollet, Sen Liu et al.
Journal of Synchrotron Radiation
Advanced X-ray Imaging Techniques
article

High-resolution in situ characterization of laser powder bed fusion via transmission X-ray microscopy at X-ray free-electron lasers

Matthew Seaberg, Zane Taylor, Matthieu Chollet, Sen Liu, Leora E. Dresselhaus‐Marais, Rachel Margraf, Tharun Reddy, Christopher J. Tassone, Vivek Thampy, Lichao Fang, Aliaksei Halavanau, Patrick L. Kramer, Cynthia Melendrez, Gourab Chatterjee, Lauren Moghimi, Yifan Wang, Matthew S. Dayton, Frank Seiboth, Philip Hart, Wenxin Wang, Sara J. Irvine, Abigail D. Wilson, Kento Katagiri, Ilana J. Porter, Jade Stanton, Morten Haubro, Ying Chen, C. M. Gee, Patrick Oppermann, Silke Nelson, Tim van Driel, Franz Josef Decker, Dayeeta Pal, Kelsey Banta
article en

Abstract

In this work, we describe the instrumentation used to perform the first operando transmission X-ray microscopy (TXM) and simultaneous X-ray diffraction of laser melting simulating laser powder bed fusion on the XCS instrument at the Linac Coherent Light Source (LCLS) X-ray free-electron laser (XFEL). Our TXM with 40× magnification in the X-ray regime at 11 keV gave spatial resolutions down to 940 nm per line pair, with effective pixel sizes down to 206 nm, image integration times of <100 fs, and frame rates tunable between 2.1 and 119 ns for two probe frames (0.48 GHz to 8.4 MHz). Images were recorded on Zyla and Icarus (UXI) detectors to trade off between spatial resolution and time dynamics. A 1 kW CW IR laser was coupled into the interaction point to conduct pump-probe studies of laser melting and solidification dynamics. Our temporal and spatial resolution with attenuation-based contrast exceeds that currently possible with synchrotron-based high-speed radiography. This system was sensitive to feature velocities of 10-12000 m s<sup>-1</sup> but we did not observe any motion in this range in the laser melting of Al6061 alloy. Shockwaves were not observed and hot cracking proceeded at velocities below the detection limits. Pore accumulation was observed between successive shots, indicating that bubble escape mechanisms were not active. With proper experimental design, the spatial resolution, contrast and field of view could be further improved or modified. The increased brightness and narrower bandwidth of the XFEL allowed for this imaging technique and it lays the groundwork for a wide range of operando techniques to study additive manufacturing.

Journal of Synchrotron RadiationVol. 32(3)
Deutsches Elektronen-Synchrotron DESY (DE), SLAC National Accelerator Laboratory (US), Advanced Research Systems (US), Stanford Synchrotron Radiation Lightsource (US), Linac Coherent Light Source (US), Technical University of Denmark (DK), Stanford University (US)
National Science Foundation, U.S. Department of Energy, Louisiana Board of Regents, Office of Science, National Nuclear Security Administration, Basic Energy Sciences, SLAC National Accelerator Laboratory
Openalex Percentile: Top 92%
Advanced X-ray Imaging Techniques
DOIOpen Access PDFOpenAlex
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