skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Microstructural control in metal laser powder bed fusion additive manufacturing using laser beam shaping strategy

Abstract

Additive manufacturing (AM) promises to revolutionize manufacturing by producing complex parts with tailored mechanical properties through local microstructure control. The main challenge is to control or prevent columnar (elongated) growth morphology which is prevalent in AM parts. Here, we elucidate mechanisms of microstructure control that promote favorable equiaxed grains (aspect ratio close to 1) using a laser beam shaping strategy. This requires an accurate thermal profile that is only captured using advanced predictive simulation that couples full laser ray tracing, ultra-fast hydrodynamic melt flow and the cellular automata method for grain growth. We investigate columnar to equiaxed microstructure transition during single-track laser powder bed fusion processing of 316 L stainless steel using Gaussian (circular) and elliptical (transverse and longitudinal) laser beam shapes. We demonstrate that the propensity to produce equiaxed grains through nucleation events correlates with large beam width as delivered by an elliptical transverse laser beam. In addition, we reveal different microstructure evolution mechanisms during transient states such as at start and end of a scan track when the laser is respectively turned on and off. Columnar growth is hard to prevent at the start of a track and the growth morphology in the absence of heat input ismore » dictated by the melt pool width and depth achieved and the degree of thermal undercooling. Here, we expect this fundamental understanding of the physics of local beam shaping for microstructural control would have implications on future complex beam shape designs as well as beam modulation.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1592992
Report Number(s):
LLNL-JRNL-782838
Journal ID: ISSN 1359-6454; 977939
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 184; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Additive manufacturing; Laser powder-bed fusion; Microstructure control; Beam shaping; Computer simulation

Citation Formats

Shi, Rongpei, Khairallah, Saad A., Roehling, Tien T., Heo, Tae Wook, McKeown, Joseph T., and Matthews, Manyalibo J. Microstructural control in metal laser powder bed fusion additive manufacturing using laser beam shaping strategy. United States: N. p., 2019. Web. doi:10.1016/j.actamat.2019.11.053.
Shi, Rongpei, Khairallah, Saad A., Roehling, Tien T., Heo, Tae Wook, McKeown, Joseph T., & Matthews, Manyalibo J. Microstructural control in metal laser powder bed fusion additive manufacturing using laser beam shaping strategy. United States. doi:10.1016/j.actamat.2019.11.053.
Shi, Rongpei, Khairallah, Saad A., Roehling, Tien T., Heo, Tae Wook, McKeown, Joseph T., and Matthews, Manyalibo J. Fri . "Microstructural control in metal laser powder bed fusion additive manufacturing using laser beam shaping strategy". United States. doi:10.1016/j.actamat.2019.11.053. https://www.osti.gov/servlets/purl/1592992.
@article{osti_1592992,
title = {Microstructural control in metal laser powder bed fusion additive manufacturing using laser beam shaping strategy},
author = {Shi, Rongpei and Khairallah, Saad A. and Roehling, Tien T. and Heo, Tae Wook and McKeown, Joseph T. and Matthews, Manyalibo J.},
abstractNote = {Additive manufacturing (AM) promises to revolutionize manufacturing by producing complex parts with tailored mechanical properties through local microstructure control. The main challenge is to control or prevent columnar (elongated) growth morphology which is prevalent in AM parts. Here, we elucidate mechanisms of microstructure control that promote favorable equiaxed grains (aspect ratio close to 1) using a laser beam shaping strategy. This requires an accurate thermal profile that is only captured using advanced predictive simulation that couples full laser ray tracing, ultra-fast hydrodynamic melt flow and the cellular automata method for grain growth. We investigate columnar to equiaxed microstructure transition during single-track laser powder bed fusion processing of 316 L stainless steel using Gaussian (circular) and elliptical (transverse and longitudinal) laser beam shapes. We demonstrate that the propensity to produce equiaxed grains through nucleation events correlates with large beam width as delivered by an elliptical transverse laser beam. In addition, we reveal different microstructure evolution mechanisms during transient states such as at start and end of a scan track when the laser is respectively turned on and off. Columnar growth is hard to prevent at the start of a track and the growth morphology in the absence of heat input is dictated by the melt pool width and depth achieved and the degree of thermal undercooling. Here, we expect this fundamental understanding of the physics of local beam shaping for microstructural control would have implications on future complex beam shape designs as well as beam modulation.},
doi = {10.1016/j.actamat.2019.11.053},
journal = {Acta Materialia},
number = C,
volume = 184,
place = {United States},
year = {2019},
month = {11}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share: