Keywords and Phrases
Additive manufacturing; Laser powder bed fusion (LPBF); Selective laser melting (SLM); Solidification; Undercooling; X-ray imaging
"Fusion-based metal additive manufacturing (AM) has garnered much interest in recent decades. Despite the popularity of fusion-based AM technologies such as selective laser melting (SLM), there are still fundamental questions and uncertainties that need to be addressed. In this work, we focus on the understanding of the undercooling in the SLM process and the uncertainties induced by the laser beam size, power, and scan speed. First, we report the estimation of undercooling in the SLM process from the solidification rate measured by in-situ high-speed synchrotron x-ray imaging, based on the dendrite growth velocity model. The undercooling changes as a function of location and time as the solidification front proceeds to the surface of the melt pool. A general increasing trend is observed for AlSi10Mg, while a general decreasing trend is observed for Ti6Al4V. The opposite overall evolution trend of the undercooling for the two AM materials is attributed to the ratio of the latent heat to heat capacity and the thermal diffusivity. The temporal and spatial variation of the undercooling and the dependence of undercooling evolution trend on material properties revealed here are important for understanding microstructure evolution in fusion-based metal AM. Second, the uncertainties in the SLM process due to variations of laser beam size, power, and scan speed from the optimized values are identified by in-situ x-ray imaging and the leading cause of uncertainty is revealed. A small ( < 5%) variation in the laser beam size, power, and scan speed results in linear variations in the depression zone, melt pool, and spatter behavior. The variation in the SLM dynamics identified in this work is important for understanding the sensitivity of the SLM process to the laser processing parameters"--Abstract, page iv.
Liou, Frank W.
Mechanical and Aerospace Engineering
M.S. in Manufacturing Engineering
National Science Foundation (U.S.)
Missouri University of Science and Technology. Center for Aerospace Manufacturing Technologies (CAMT)
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Undercooling in laser powder bed fusion metal additive manufacturing
- Sources of uncertainty induced by laser processing parameters in selective laser melting of Ti6Al4V
xi, 73 pages
© 2020 Meelap Michael Coday, All rights reserved.
Thesis - Open Access
Electronic OCLC #
Coday, Meelap M., "In-situ x-ray imaging of the selective laser melting process" (2020). Masters Theses. 7930.