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Search Publications by: Andrew J Allen (Fed)

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Displaying 51 - 75 of 257

Simulation of TTT curves for additively manufactured Inconel 625

January 1, 2019
Author(s)
Carelyn E. Campbell, Greta Lindwall, Eric Lass, Fan Zhang, Mark R. Stoudt, Andrew J. Allen, Lyle E. Levine
The ability to use common computational thermodynamic and kinetic tools to study the microstructure evolution in Inconel 625 (IN625) manufactured using the additive manufacturing (AM) technique of laser powder-bed fusion is evaluated. Solidification

Transformation of Engineered Nanomaterials through the Prism of Silver Sulfidation

January 1, 2019
Author(s)
Fan Zhang, Andrew J. Allen, Aaron C. Johnston-Peck, Jingyu Liu, John M. Pettibone
Structure transformation of engineered nanomaterials (ENMs) often dictates their efficacy, safety, and environmental impact. To address the existing significant knowledge gap regarding the fundamental kinetic rate and extent of ENMs transformation in

High-efficiency Coherence-Preserving Harmonic Rejection with Crystal Optics

September 1, 2018
Author(s)
Fan Zhang, Andrew J. Allen, Lyle E. Levine, Gabrielle G. Long, Ivan Kuzmenko, Jan Ilavsky
We report a harmonic rejection scheme based on the combination of Si (111) monochromator and Si (220) harmonic-rejection crystal optics. This approach is of importance to a wide range of X- ray applications in all three major branches of modern X-ray

Effect of Heat Treatment on the Microstructural Evolution of a Nickel-Based Superalloy Additive-Manufactured by Powder Bed Fusion Laser Sintering

June 15, 2018
Author(s)
Fan Zhang, Lyle E. Levine, Andrew J. Allen, Mark R. Stoudt, Greta Lindwall, Eric Lass, Maureen E. Williams, Yaakov S. Idell, Carelyn E. Campbell
Elemental segregation is a ubiquitous phenomenon in additive-manufactured (AM) parts due to solute rejection and redistribution during the rapid solidification process. Using electron microscopy, in situ synchrotron X-ray scattering and diffraction, and

Development of combined microstructure and structure characterization facility for in situ and operando studies at the Advanced Photon Source

June 1, 2018
Author(s)
Jan Ilavsky, Fan Zhang, Ross N. Andrews, Ivan Kuzmenko, Pete R. Jemian, Lyle E. Levine, Andrew J. Allen
Following many years of evolutionary development, first at the National Synchrotron Light Source, Brookhaven National Laboratory, and then at the Advanced Photon Source (APS), Argonne National Laboratory, the APS ultra-small-angle X-ray scattering (USAXS)

Journal of Applied Crystallography: The First 50 Years and Beyond

April 1, 2018
Author(s)
Andrew J. Allen, Janos Hajdu, Garry J. McIntyre
The first issue of the Journal of Applied Crystallography appeared in April 1968. So, with this issue we celebrate its 50th birthday! We should start by expressing our appreciation for all the readers, authors, reviewers, editors and technical staff who

In situ Angstrom-to-Micrometer Characterization of the Structural and Microstructural Changes in Kaolinite on Heating using Ultra-Small-Angle, Small-Angle, and Wide-Angle X-ray Scattering (USAXS/SAXS/WAXS)

September 26, 2017
Author(s)
Fan Zhang, Andrew J. Allen, Greeshma Gadikota
In this study, synchrotron-based in-operando multi-scale X-ray scattering analyses are used to connect the microstructural changes to the phase changes in kaolinite on heating from 30 °C to 1150 °C. Combined ultra-small-angle and small-angle X-ray

Application of Finite Element, Phase-field, and CALPHAD-based Methods to Additive Manufacturing of Ni-based Superalloys

September 21, 2017
Author(s)
Trevor Keller, Greta Lindwall, Supriyo Ghosh, Li Ma, Brandon M. Lane, Fan Zhang, Ursula R. Kattner, Eric Lass, Yaakov S. Idell, Maureen E. Williams, Andrew J. Allen, Jonathan E. Guyer, Lyle E. Levine
Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element