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Title: Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing

Abstract

Laser powder bed fusion (LPBF) is a method of additive manufacturing characterized by the rapid scanning of a high powered laser over a thin bed of metallic powder to create a single layer, which may then be built upon to form larger structures. Much of the melting, resolidification, and subsequent cooling take place at much higher rates and with much higher thermal gradients than in traditional metallurgical processes, with much of this occurring below the surface. We have used in situ high speed X-ray diffraction to extract subsurface cooling rates following resolidification from the melt and above the $β$-transus in titanium alloy Ti-6Al-4V. We observe an inverse relationship with laser power and bulk cooling rates. The measured cooling rates are seen to correlate to the level of residual strain borne by the minority $β$-Ti phase with increased strain at slower cooling rates. The $α$-Ti phase shows a lattice contraction which is invariant with cooling rate. We also observe a broadening of the diffraction peaks which is greater for the $β$-Ti phase at slower cooling rates and a change in the relative phase fraction following LPBF. These results provide a direct measure of the subsurface thermal history and demonstrate its importancemore » to the ultimate quality of additively manufactured materials.« less

Authors:
 [1];  [1];  [2];  [2];  [2];  [2];  [1];  [2];  [3];  [3];  [2]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [3];  [2];  [1]; ORCiD logo [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Ames Lab., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1600506
Alternate Identifier(s):
OSTI ID: 1604284
Report Number(s):
[IS-J-10156; LLNL-JRNL-758994]
[Journal ID: ISSN 2045-2322]
Grant/Contract Number:  
[AC02-07CH11358; AC02-76SF00515; AC52-07NA27344]
Resource Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
[ Journal Volume: 10; Journal Issue: 1]; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Characterization and analytical techniques; Metals and alloys; Materials science

Citation Formats

Thampy, Vivek, Fong, Anthony Y., Calta, Nicholas P., Wang, Jenny, Martin, Aiden A., Depond, Philip J., Kiss, Andrew M., Guss, Gabe, Xing, Qingfeng, Ott, Ryan T., van Buuren, Anthony, Toney, Michael F., Weker, Johanna Nelson, Kramer, Matthew J., Matthews, Manyalibo J., Tassone, Christopher J., and Stone, Kevin H. Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing. United States: N. p., 2020. Web. doi:10.1038/s41598-020-58598-z.
Thampy, Vivek, Fong, Anthony Y., Calta, Nicholas P., Wang, Jenny, Martin, Aiden A., Depond, Philip J., Kiss, Andrew M., Guss, Gabe, Xing, Qingfeng, Ott, Ryan T., van Buuren, Anthony, Toney, Michael F., Weker, Johanna Nelson, Kramer, Matthew J., Matthews, Manyalibo J., Tassone, Christopher J., & Stone, Kevin H. Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing. United States. doi:10.1038/s41598-020-58598-z.
Thampy, Vivek, Fong, Anthony Y., Calta, Nicholas P., Wang, Jenny, Martin, Aiden A., Depond, Philip J., Kiss, Andrew M., Guss, Gabe, Xing, Qingfeng, Ott, Ryan T., van Buuren, Anthony, Toney, Michael F., Weker, Johanna Nelson, Kramer, Matthew J., Matthews, Manyalibo J., Tassone, Christopher J., and Stone, Kevin H. Thu . "Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing". United States. doi:10.1038/s41598-020-58598-z. https://www.osti.gov/servlets/purl/1600506.
@article{osti_1600506,
title = {Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing},
author = {Thampy, Vivek and Fong, Anthony Y. and Calta, Nicholas P. and Wang, Jenny and Martin, Aiden A. and Depond, Philip J. and Kiss, Andrew M. and Guss, Gabe and Xing, Qingfeng and Ott, Ryan T. and van Buuren, Anthony and Toney, Michael F. and Weker, Johanna Nelson and Kramer, Matthew J. and Matthews, Manyalibo J. and Tassone, Christopher J. and Stone, Kevin H.},
abstractNote = {Laser powder bed fusion (LPBF) is a method of additive manufacturing characterized by the rapid scanning of a high powered laser over a thin bed of metallic powder to create a single layer, which may then be built upon to form larger structures. Much of the melting, resolidification, and subsequent cooling take place at much higher rates and with much higher thermal gradients than in traditional metallurgical processes, with much of this occurring below the surface. We have used in situ high speed X-ray diffraction to extract subsurface cooling rates following resolidification from the melt and above the $β$-transus in titanium alloy Ti-6Al-4V. We observe an inverse relationship with laser power and bulk cooling rates. The measured cooling rates are seen to correlate to the level of residual strain borne by the minority $β$-Ti phase with increased strain at slower cooling rates. The $α$-Ti phase shows a lattice contraction which is invariant with cooling rate. We also observe a broadening of the diffraction peaks which is greater for the $β$-Ti phase at slower cooling rates and a change in the relative phase fraction following LPBF. These results provide a direct measure of the subsurface thermal history and demonstrate its importance to the ultimate quality of additively manufactured materials.},
doi = {10.1038/s41598-020-58598-z},
journal = {Scientific Reports},
number = [1],
volume = [10],
place = {United States},
year = {2020},
month = {2}
}

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