Tao Sun1
University of Virginia1
Additive manufacturing (AM) is transforming many industries and revolutionizing the way we build things. The global pandemic once again highlights the significance of digital on-site on-demand manufacturing and short supply chain. There are tens of AM technologies, which can be classified into seven categories. Most of these processes are conceptually simple; however, complex energy-matter interactions are involved which induce phenomena that occur in microsecond timescale or faster. Probing and understanding these phenomena are critical for solving the long-standing problems in AM, which, include but not limited to, substantial structure defects, inadequate build repeatability and reliability, lack of high-fidelity models, and limited feedstock materials. In the last few years, we applied high-speed synchrotron x-ray imaging and diffraction techniques for operando studies of laser powder bed fusion, directed energy deposition, and binder jetting processes. High-flux high-energy x-ray beam afforded by the 3<sup>rd</sup>-generation hard x-ray facility and the state-of-the-art detection systems enable direct imaging of structure dynamics underneath sample surface with MHz frame rate, hundred picoseconds temporal resolution, and micrometer spatial resolution. The rapid melting and solidification, particles spattering, porosity and crack formation in laser AM can be observed with unprecedented details. In binder jetting, the powder motions induced by droplet impact can also be quantified. These operando synchrotron experiments allow us to answer many fundamental questions in AM. In addition, the direct observation and measurement of the dynamic structure evolution promote the development of numerical models, as well as the real-time monitoring techniques based on lab-scale sensors.