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Title: On the evolution of microstructure and defect control in 316L SS components fabricated via directed energy deposition

Abstract

To identify the critical issues that affect the evolution of microstructure during additive manufacturing, we investigated the influence of process parameters on the evolution of the dimensional and surface quality, microstructure, internal defects, and mechanical properties in 316L stainless steel (SS) components fabricated using laser engineered net shaping (LENS®), a directed energy deposition (DED) additive manufacturing (AM) technique. The results show that the accumulation of un-melted powder particles on the side walls of deposited sections can be avoided by selecting a laser under-focused condition. Moreover, we report that the variation of melt pool width is more sensitive to laser power than to the depth of the melt pool. The formation of a so-called “hierarchical” microstructure with cellular morphology is attributable to a combination of layer deposition and rapid solidification, which are characteristics of AM. Finally, we discuss microstructure evolution and defect formation, particularly the formation of multiple interfaces and the presence of un-melted powder particles and pores, in light of the dynamic convective fluid flow and rapid solidification that occur in the melt pool. X-ray computed tomography (X-CT) was used to precisely map the spatial distribution of pores in the DED components. The evolution of microstructure during DED is discussedmore » in the context of related thermal phenomena in an effort to provide fundamental insight into the mechanisms that govern defect formation.« less

Authors:
 [1];  [1];  [2];  [2];  [1];  [1];  [1];  [1]
  1. Univ. of California, Irvine, CA (United States)
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1559510
Alternate Identifier(s):
OSTI ID: 1563048
Report Number(s):
SAND2019-9333J
Journal ID: ISSN 0921-5093; 678327
Grant/Contract Number:  
AC04-94AL85000; NA0003525
Resource Type:
Accepted Manuscript
Journal Name:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
Additional Journal Information:
Journal Volume: 764; Journal Issue: C; Journal ID: ISSN 0921-5093
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Zheng, B., Haley, J. C., Yang, N., Yee, J., Terrassa, K. W., Zhou, Y., Lavernia, E. J., and Schoenung, J. M. On the evolution of microstructure and defect control in 316L SS components fabricated via directed energy deposition. United States: N. p., 2019. Web. doi:10.1016/j.msea.2019.138243.
Zheng, B., Haley, J. C., Yang, N., Yee, J., Terrassa, K. W., Zhou, Y., Lavernia, E. J., & Schoenung, J. M. On the evolution of microstructure and defect control in 316L SS components fabricated via directed energy deposition. United States. doi:10.1016/j.msea.2019.138243.
Zheng, B., Haley, J. C., Yang, N., Yee, J., Terrassa, K. W., Zhou, Y., Lavernia, E. J., and Schoenung, J. M. Mon . "On the evolution of microstructure and defect control in 316L SS components fabricated via directed energy deposition". United States. doi:10.1016/j.msea.2019.138243.
@article{osti_1559510,
title = {On the evolution of microstructure and defect control in 316L SS components fabricated via directed energy deposition},
author = {Zheng, B. and Haley, J. C. and Yang, N. and Yee, J. and Terrassa, K. W. and Zhou, Y. and Lavernia, E. J. and Schoenung, J. M.},
abstractNote = {To identify the critical issues that affect the evolution of microstructure during additive manufacturing, we investigated the influence of process parameters on the evolution of the dimensional and surface quality, microstructure, internal defects, and mechanical properties in 316L stainless steel (SS) components fabricated using laser engineered net shaping (LENS®), a directed energy deposition (DED) additive manufacturing (AM) technique. The results show that the accumulation of un-melted powder particles on the side walls of deposited sections can be avoided by selecting a laser under-focused condition. Moreover, we report that the variation of melt pool width is more sensitive to laser power than to the depth of the melt pool. The formation of a so-called “hierarchical” microstructure with cellular morphology is attributable to a combination of layer deposition and rapid solidification, which are characteristics of AM. Finally, we discuss microstructure evolution and defect formation, particularly the formation of multiple interfaces and the presence of un-melted powder particles and pores, in light of the dynamic convective fluid flow and rapid solidification that occur in the melt pool. X-ray computed tomography (X-CT) was used to precisely map the spatial distribution of pores in the DED components. The evolution of microstructure during DED is discussed in the context of related thermal phenomena in an effort to provide fundamental insight into the mechanisms that govern defect formation.},
doi = {10.1016/j.msea.2019.138243},
journal = {Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing},
number = C,
volume = 764,
place = {United States},
year = {2019},
month = {9}
}

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