Researchers use high-speed X-ray imaging to capture microscopic flaws in AM process
June 17, 2019
Researchers from Missouri University of Science and Technology, Rolla, Missouri, USA; Argonne National Laboratory, operated by University of Chicago Argonne LLC, Lemont, Illinois, USA; and the University of Utah, USA, have reportedly created high-speed X-ray ‘movies’ of laser spattering to identify the cause of microscopic defects. Laser spattering refers to the ejection of molten metal from a pool heated by a high-power laser during laser-based manufacturing processes, such as Laser Powder Bed Fusion (L-PBF) Additive Manufacturing or laser welding.
The researchers described their findings in a paper published in the journal Physical Review X. By using X-ray imaging, the researchers captured the spattering behaviour of Ti-6Al-4V during fabrication. Their microscopic movies reveal “a novel mechanism of laser spattering – the bulk explosion of a tongue-like protrusion” that forms in one region of the metal, according to the paper, titled Bulk Explosion-Induced Metal Spattering During Laser Processing.
“The newly-discovered mechanism will guide the development of approaches to mitigate defect formation in welds and additively manufactured parts,” stated Dr Lianyi Chen, Assistant Professor of Mechanical and Aerospace Engineering at Missouri S&T and one of the paper’s authors.
Chen collaborated with Dr Tao Sun and team at Argonne National Laboratory, and Dr Wenda Tan and team at the University of Utah, on the research. The group created the images through the use of a high-energy synchrotron X-ray at Argonne National Laboratory along with image analysis and numerical simulations. Researchers at the Argonne facility employed X-ray scattering techniques to study materials.
“The high penetration power of hard X-rays and high resolutions of the imaging technique enable us, for the first time ever, to connect the spattering behaviour above the surface with dynamics below the surface and inside the titanium sample,” Chen added. Working with Chen on the research is Qilin Guo, a PhD student in mechanical engineering at Missouri S&T.