Fall 2020 Seminar Series: Tao Sun
University of Virginia
Host: Todd Hufnagel
Operando synchrotron x-ray studies of metal additive manufacturing
Metal additive manufacturing (AM) refers to a group of disruptive technologies that build metallic three-dimensional objects by adding feedstock materials layer-wise based on computer models. AM not only unleashes the design freedom of engineers by allowing the build of geometrically complex parts but also opens up tremendous opportunities for material scientists to synthesize and process novel materials with phases and microstructures far-from-equilibrium. While AM holds the promise to completely revolutionize the industry, building defect-free metal products with precise control of material microstructures and part performance remains challenging. Indeed, substantial fundamental issues exist in metal AM which need to be addressed before the technology can reach its full potential.
At the Advanced Photon Source (APS), we have been applying operando high-speed x-ray imaging and diffraction techniques to probe a variety of metal AM processes. The superior penetration power of high-energy x-rays and the extremely high fluxes afforded by the 3rd-generation synchrotron facility allow the characterization of dynamic structural evolution in bulk metallic materials with unprecedented spatial and temporal resolutions. Many highly transient phenomena that take place during the energy-matter interaction in metal AM processes were investigated, and the mechanisms responsible for different types of defects were identified.
In the presentation, I will give a brief overview of the operando synchrotron x-ray studies of various metal AM processes (i.g. laser powder bed fusion, directed energy deposition, and binder jetting), performed at the APS in the last few years. The new insights into metal AM gained from these operando synchrotron experiments will be highlighted. Furthermore, I will elucidate how the direct observations enabled by x-ray imaging helped us understand the mechanisms of defect formation and elimination, calibrate and validate numerical models, and improve the build reliability and repeatability.