Publication Date
10-2019
Department
Ames Laboratory
Campus Units
Ames Laboratory
OSTI ID+
1560679
Report Number
IS-J 10010, LLNL-JRNL-748807
DOI
10.1002/adem.201900455
Journal Title
Advanced Energy Materials
Volume Number
21
Issue Number
10
First Page
1900455
Abstract
Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven by an incomplete understanding of how unique process parameters relate to defect formation and ultimately mechanical properties. To address that gap, high‐speed X‐ray imaging is used to probe subsurface melt pool dynamics and void‐formation mechanisms inaccessible to other monitoring approaches. This technique directly observes the depth and dynamic behavior of the vapor depression, also known as the keyhole depression, which is formed by recoil pressure from laser‐driven metal vaporization. Also, vapor bubble formation and motion due to melt pool currents is observed, including instances of bubbles splitting before solidification into clusters of smaller voids while the material rapidly cools. Other phenomena include bubbles being formed from and then recaptured by the vapor depression, leaving no voids in the final part. Such events complicate attempts to identify defect formation using surface‐sensitive process‐monitoring tools. Finally, once the void defects form, they cannot be repaired by simple laser scans, without introducing new defects, thus emphasizing the importance of understanding processing parameters to develop robust defect‐mitigation strategies based on experimentally validated models.
DOE Contract Number(s)
AC02-07CH11358; AC02-76SF00515; SC0012704; AC52-07NA27344
Language
en
Department of Energy Subject Categories
42 ENGINEERING; 36 MATERIALS SCIENCE
Publisher
Iowa State University Digital Repository, Ames IA (United States)
