In-situ Observations of Directed Energy Deposition Additive Manufacturing Using High-Speed X-ray Imaging
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https://doi.org/10.1007/s11837-020-04469-x Ó 2020 The Minerals, Metals & Materials Society
IN SITU SYNCHROTRON AND NEUTRON CHARACTERIZATION OF ADDITIVELY MANUFACTURED ALLOYS
In-situ Observations of Directed Energy Deposition Additive Manufacturing Using High-Speed X-ray Imaging SARAH J. WOLFF ,1,6 SAMANTHA WEBSTER,2,7 NIRANJAN D. PARAB,3,8 BENJAMIN ARONSON,4,9 BENJAMIN GOULD,4,10 AARON GRECO,4,11 and TAO SUN5,12 1.—Industrial and Systems Engineering, Texas A&M University, College Station, TX 77843, USA. 2.—Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA. 3.—X-ray Science Division, Argonne National Laboratory, Lemont, IL 60439, USA. 4.—Applied Materials Division, Argonne National Laboratory, Lemont, IL 60439, USA. 5.—Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22902, USA. 6.—e-mail: [email protected]. 7.—e-mail: [email protected]. 8.—e-mail: [email protected]. 9.—e-mail: [email protected]. 10.—e-mail: [email protected]. 11.—e-mail: [email protected]. 12.—e-mail: [email protected]
In laser-based directed energy deposition (DED) additive manufacturing, interactions among the laser beam, particle flow, and melt pool influence the properties of the solidified final part. Two separate DED systems, one with high powder flow rates to represent industrial-scale DED processing and the other with low powder flow rates for individual particle tracking, were synchronized with the high-speed imaging setup at the Advanced Photon Source in Argonne National Laboratory. In-situ x-ray imaging of the DED process using both systems highlighted the influence of powder flow rates. Increased powder flow rates resulted in less laser absorption into the melt pool, leading to a transition from a keyhole mode to a melt pool without a keyhole but with surface fluctuations due to powder flow. Increased velocities of particles during powder flow resulted in a decrease in particle melting times and a greater propensity for porosity formation. Overall, better understanding of the interactions that occur during various scales of the DED process will enable flexibility, control, and new materials development in DED-based additive manufacturing.
INTRODUCTION Directed energy deposition (DED) additive manufacturing (AM) is a promising process that has the capability to fabricate multi-material parts with controlled microstructures due to the localized directional solidification of deposited powders of various metallic alloys. The unique phase transformations during the process provide an opportunity to design novel materials that take advantage of the physical conditions that occur during melting and solidification.1 The laser-based DED process
Sarah J. Wolff and Samantha Webster have contributed equally to this work. (Received June 16, 2020; accepted October 23, 2020)
consists of powder flow, conveyed with an inert carrier gas, into a laser-induced melt pool.2 Most DED systems deliver powder from a coaxial nozzle that is aligned with a high-powered laser beam. Powde
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