LDRD Seminar Series: 'X-ray Vision of Metal 3D Printing'

Tao Sun

Physicist Tao Sun (XSD) will discuss his Laboratory-Directed Research and Development (LDRD) sponsored work at the LDRD Seminar Series presentation Tuesday, Dec. 12, 2017. “X-ray Vision of Metal 3D Printing” begins at 12:30 p.m. in the Building 203 Auditorium. All are welcome to attend.

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Abstract

Additive manufacturing (AM), or three-dimensional (3D) printing, refers to a suite of different processes that build up parts by adding materials one layer at a time based on 3D computer models. Compared with traditional manufacturing techniques that build by removing materials from a bulky chunk, AM creates customized complex products by adding materials together with satisfactory geometric accuracy, and thereby exhibits unique advantages, including more efficient use of raw materials, less generation of hazard waste, less consumption of energy, shorter supply chain and reduced time to market. AM largely breaks the tooling constraints by allowing optimized design and fabrication of products with extreme complexities without the need to sacrifice the part functionality for the ease of production.

During the past three decades, AM of metallic materials has advanced tremendously, particularly in the fields of medical, aerospace, automobile and defense applications. Laser powder bed fusion (LPBF) is one of the most extensively used metal AM techniques. In a typical LPBF process, a laser beam scans across a thin layer of metallic powders and locally melts the powders through to the layer below. Although the process is conceptually simple, many highly dynamic and transient physical phenomena are involved because of the extremely high heating and cooling rates (e.g., melting and partial vaporization of metallic powders, flow of the melt pool, powder ejection, rapid solidification, nonequilibrium phase transition). Oftentimes, the complex interactions among these processes result in a product with a rough surface, significant porosity, large residual stress, and/or unfavorable phase and grain structures.

To understand the mechanisms responsible for the formation of these microstructural defects, our LDRD project team built a small laser AM apparatus and carried out high-speed X-ray imaging and diffraction experiments at the 32-ID-B beamline of the Advanced Photon Source. We demonstrated that quantitative information on melt pool dynamics, powder flow velocity, solidification rate, and phase transformation can be obtained from the time-resolved X-ray images and diffraction patterns. The experimental and data analysis approaches we developed in this project enabled the first-ever observation of the LPBF process with unprecedented spatial and temporal resolutions. The results from the high-speed X-ray experiments are helping researchers not only understand the physics underpinning the formation of different structural defects, but also build high-fidelity computer models to guide the process optimization for manufacturing parts with different geometries and dimensions.

Biography

Tao Sun has worked at Argonne’s Advanced Photon Source (APS) since 2005, and is now a physicist in the X-ray Science Division (XSD). He received his bachelor and master degrees in materials science and engineering from Tsinghua University in 2002 and 2004, respectively. Sun received his Ph.D. in materials science and engineering from Northwestern University. His thesis research on nanostructured oxides was supported by Argonne’s Graduate Program under the supervision of Vinayak Dravid and Jin Wang. After graduation in 2009, he joined the Time-Resolved Research Group of XSD as a postdoc researcher, working with Murray Gibson and Wang on developing coherence electron and X-ray scattering techniques. In 2012, he became a staff scientist of the Imaging Group of XSD, and started to co-manage the 32-ID beamline of the APS. Sun’s research covers a broad range of topics in materials science and X-ray physics. His current projects focus on developing and applying cutting-edge synchrotron X-ray imaging and scattering techniques to understand highly dynamic processes in hard and soft condensed matters, e.g. laser-metal interaction in the additive manufacturing processes. Sun has been serving as committee members of Broader Impact Program Development and Meeting Assessment subcommittees of the Materials Research Society. He is a fellow of the Northwestern-Argonne Institute for Science and Engineering.

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