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Title: Critical instability at moving keyhole tip generates porosity in laser melting

Abstract

Laser powder bed fusion is a dominant metal 3D printing technology. However, porosity defects remain a challenge for fatigue-sensitive applications. Some porosity is associated with deep and narrow vapor depressions called keyholes, which occur under high-power, low–scan speed laser melting conditions. High-speed x-ray imaging enables operando observation of the detailed formation process of pores in Ti-6Al-4V caused by a critical instability at the keyhole tip. We found that the boundary of the keyhole porosity regime in power-velocity space is sharp and smooth, varying only slightly between the bare plate and powder bed. The critical keyhole instability generates acoustic waves in the melt pool that provide additional yet vital driving force for the pores near the keyhole tip to move away from the keyhole and become trapped as defects.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [5]
  1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China., Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084, China.
  2. X-ray Science Division, Argonne National Laboratory, Lemont, IL 60439, USA.
  3. Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA.
  4. Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA., NextManufacturing Center, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
  5. Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904, USA.
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1724317
Resource Type:
Published Article
Journal Name:
Science
Additional Journal Information:
Journal Name: Science Journal Volume: 370 Journal Issue: 6520; Journal ID: ISSN 0036-8075
Publisher:
American Association for the Advancement of Science (AAAS)
Country of Publication:
United States
Language:
English

Citation Formats

Zhao, Cang, Parab, Niranjan D., Li, Xuxiao, Fezzaa, Kamel, Tan, Wenda, Rollett, Anthony D., and Sun, Tao. Critical instability at moving keyhole tip generates porosity in laser melting. United States: N. p., 2020. Web. https://doi.org/10.1126/science.abd1587.
Zhao, Cang, Parab, Niranjan D., Li, Xuxiao, Fezzaa, Kamel, Tan, Wenda, Rollett, Anthony D., & Sun, Tao. Critical instability at moving keyhole tip generates porosity in laser melting. United States. https://doi.org/10.1126/science.abd1587
Zhao, Cang, Parab, Niranjan D., Li, Xuxiao, Fezzaa, Kamel, Tan, Wenda, Rollett, Anthony D., and Sun, Tao. Thu . "Critical instability at moving keyhole tip generates porosity in laser melting". United States. https://doi.org/10.1126/science.abd1587.
@article{osti_1724317,
title = {Critical instability at moving keyhole tip generates porosity in laser melting},
author = {Zhao, Cang and Parab, Niranjan D. and Li, Xuxiao and Fezzaa, Kamel and Tan, Wenda and Rollett, Anthony D. and Sun, Tao},
abstractNote = {Laser powder bed fusion is a dominant metal 3D printing technology. However, porosity defects remain a challenge for fatigue-sensitive applications. Some porosity is associated with deep and narrow vapor depressions called keyholes, which occur under high-power, low–scan speed laser melting conditions. High-speed x-ray imaging enables operando observation of the detailed formation process of pores in Ti-6Al-4V caused by a critical instability at the keyhole tip. We found that the boundary of the keyhole porosity regime in power-velocity space is sharp and smooth, varying only slightly between the bare plate and powder bed. The critical keyhole instability generates acoustic waves in the melt pool that provide additional yet vital driving force for the pores near the keyhole tip to move away from the keyhole and become trapped as defects.},
doi = {10.1126/science.abd1587},
journal = {Science},
number = 6520,
volume = 370,
place = {United States},
year = {2020},
month = {11}
}

Journal Article:
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