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Title: Ultrafast dynamics of laser-metal interactions in additive manufacturing alloys captured by in situ X-ray imaging

Abstract

Advanced in situ characterization is essential for determining the underlying dynamics of laser-material interactions central to both laser welding and the rapidly expanding field of additive manufacturing. Traditional characterization techniques leave a critical experimental gap in understanding the complex subsurface fluid flow and metal evaporation dynamics inherent in laser-induced heating of the metal. Herein, in situ ultra-high-speed transmission X-ray imaging is revealed to be essential for bridging this information gap, particularly via comparison with and validation of advanced multiphysics simulations. Imaging on submicrosecond timescales enables correlation between dynamics of the laser-generated vapor–liquid interface and melt pool surface instabilities in industrially relevant alloys. X-ray imaging and complimentary simulations reveal vapor depression oscillations and rapid expansion due to reflection of the processing laser from the front surface of the vapor depression. Pore formation studies at steady state and during prompt removal of laser heating at the end of track reveal that the rapidly solidifying melt pool traps pores near the base of the vapor-filled depression. Moreover, pores within the melt pool are entrained by Marangoni convection which overcomes the force of buoyancy and forces the pores downward from the surface immediately before solidification. Observed solidification kinetics, consistent with previous results, give insightmore » into surface morphology and porosity in the processed material. The information presented here is key for defining the physical models that describe laser-material interaction and ultimately increases our understanding of the emerging field of laser-based metal additive manufacturing.« less

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Washington State Univ., Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); LLNL Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP) (NA-10)
OSTI Identifier:
1547737
Alternate Identifier(s):
OSTI ID: 1515344; OSTI ID: 1542979
Report Number(s):
LLNL-JRNL-756599
Journal ID: ISSN 2590-0498; S2590049818300419; 100002; PII: S2590049818300419
Grant/Contract Number:  
AC52–07NA27344; NA0002442; AC02-06CH11357; AC52-07NA27344
Resource Type:
Published Article
Journal Name:
Materials Today Advances
Additional Journal Information:
Journal Name: Materials Today Advances Journal Volume: 1 Journal Issue: C; Journal ID: ISSN 2590-0498
Publisher:
Elsevier
Country of Publication:
United Kingdom
Language:
English
Subject:
additive manufacturing; laser processing; X-ray imaging; multiphysics simulation; pore formation; 36 MATERIALS SCIENCE

Citation Formats

Martin, Aiden A., Calta, Nicholas P., Hammons, Joshua A., Khairallah, Saad A., Nielsen, Michael H., Shuttlesworth, Richard M., Sinclair, Nicholas, Matthews, Manyalibo J., Jeffries, Jason R., Willey, Trevor M., and Lee, Jonathan R. I. Ultrafast dynamics of laser-metal interactions in additive manufacturing alloys captured by in situ X-ray imaging. United Kingdom: N. p., 2019. Web. doi:10.1016/j.mtadv.2019.01.001.
Martin, Aiden A., Calta, Nicholas P., Hammons, Joshua A., Khairallah, Saad A., Nielsen, Michael H., Shuttlesworth, Richard M., Sinclair, Nicholas, Matthews, Manyalibo J., Jeffries, Jason R., Willey, Trevor M., & Lee, Jonathan R. I. Ultrafast dynamics of laser-metal interactions in additive manufacturing alloys captured by in situ X-ray imaging. United Kingdom. doi:10.1016/j.mtadv.2019.01.001.
Martin, Aiden A., Calta, Nicholas P., Hammons, Joshua A., Khairallah, Saad A., Nielsen, Michael H., Shuttlesworth, Richard M., Sinclair, Nicholas, Matthews, Manyalibo J., Jeffries, Jason R., Willey, Trevor M., and Lee, Jonathan R. I. Fri . "Ultrafast dynamics of laser-metal interactions in additive manufacturing alloys captured by in situ X-ray imaging". United Kingdom. doi:10.1016/j.mtadv.2019.01.001.
@article{osti_1547737,
title = {Ultrafast dynamics of laser-metal interactions in additive manufacturing alloys captured by in situ X-ray imaging},
author = {Martin, Aiden A. and Calta, Nicholas P. and Hammons, Joshua A. and Khairallah, Saad A. and Nielsen, Michael H. and Shuttlesworth, Richard M. and Sinclair, Nicholas and Matthews, Manyalibo J. and Jeffries, Jason R. and Willey, Trevor M. and Lee, Jonathan R. I.},
abstractNote = {Advanced in situ characterization is essential for determining the underlying dynamics of laser-material interactions central to both laser welding and the rapidly expanding field of additive manufacturing. Traditional characterization techniques leave a critical experimental gap in understanding the complex subsurface fluid flow and metal evaporation dynamics inherent in laser-induced heating of the metal. Herein, in situ ultra-high-speed transmission X-ray imaging is revealed to be essential for bridging this information gap, particularly via comparison with and validation of advanced multiphysics simulations. Imaging on submicrosecond timescales enables correlation between dynamics of the laser-generated vapor–liquid interface and melt pool surface instabilities in industrially relevant alloys. X-ray imaging and complimentary simulations reveal vapor depression oscillations and rapid expansion due to reflection of the processing laser from the front surface of the vapor depression. Pore formation studies at steady state and during prompt removal of laser heating at the end of track reveal that the rapidly solidifying melt pool traps pores near the base of the vapor-filled depression. Moreover, pores within the melt pool are entrained by Marangoni convection which overcomes the force of buoyancy and forces the pores downward from the surface immediately before solidification. Observed solidification kinetics, consistent with previous results, give insight into surface morphology and porosity in the processed material. The information presented here is key for defining the physical models that describe laser-material interaction and ultimately increases our understanding of the emerging field of laser-based metal additive manufacturing.},
doi = {10.1016/j.mtadv.2019.01.001},
journal = {Materials Today Advances},
number = C,
volume = 1,
place = {United Kingdom},
year = {2019},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1016/j.mtadv.2019.01.001

Figures / Tables:

Figure 1 Figure 1: Schematic of experimental configuration and X-ray imaging of laser-metal interaction. a) A metal sheet is sandwiched between two 300 µm thick glassy carbon plates. During laser irradiation, X-ray transmission images are captured using a synchrotron X-ray source and high-speed scintillator-based detector. b) X-ray imaging performed during irradiation ofmore » a 635 µm thick Al6061 substrate under an argon environment with a 400 W, 1070 nm, CW fiber laser focused to approximately 50 µm at a laser scan speed of 800 mm s-1 from left to right of the frame. The exposure time per image was 300 ns with zero delay between successive images. Lighter areas in the images indicate reduced material density.« less

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