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    University - Student Department: Materials Science and Engineering Position: Graduate

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  • Mail Code: 4034

All Publications

  • High-resolution in situ characterization of laser powder bed fusion via transmission X-ray microscopy at X-ray free-electron lasers. Journal of synchrotron radiation Taylor, Z., Reddy, T., Fang, L., Oppermann, P., Kramer, P. L., Decker, F. J., Seaberg, M., Chollet, M., van Driel, T., Halavanau, A., Hart, P., Dayton, M., Seiboth, F., Wang, W., Gee, C., Wilson, A., Margraf-O'Neal, R., Chatterjee, G., Chen, Y., Molesky, I. J., Wang, Y., Irvine, S., Stanton, J., Melendrez, C., Banta, K., Nelson, S., Thampy, V., Katagiri, K., Haubro, M., Liu, S., Pal, D., Moghimi, L., Tassone, C., Dresselhaus-Marais, L. 2025

    Abstract

    In this work, we describe the instrumentation used to perform the first operando transmission X-ray microscopy (TXM) and simultaneous X-ray diffraction of laser melting simulating laser powder bed fusion on the XCS instrument at the Linac Coherent Light Source (LCLS) X-ray free-electron laser (XFEL). Our TXM with 40× magnification in the X-ray regime at 11 keV gave spatial resolutions down to 940 nm per line pair, with effective pixel sizes down to 206 nm, image integration times of <100 fs, and frame rates tunable between 2.1 and 119 ns for two probe frames (0.48 GHz to 8.4 MHz). Images were recorded on Zyla and Icarus (UXI) detectors to trade off between spatial resolution and time dynamics. A 1 kW CW IR laser was coupled into the interaction point to conduct pump-probe studies of laser melting and solidification dynamics. Our temporal and spatial resolution with attenuation-based contrast exceeds that currently possible with synchrotron-based high-speed radiography. This system was sensitive to feature velocities of 10-12000 m s-1 but we did not observe any motion in this range in the laser melting of Al6061 alloy. Shockwaves were not observed and hot cracking proceeded at velocities below the detection limits. Pore accumulation was observed between successive shots, indicating that bubble escape mechanisms were not active. With proper experimental design, the spatial resolution, contrast and field of view could be further improved or modified. The increased brightness and narrower bandwidth of the XFEL allowed for this imaging technique and it lays the groundwork for a wide range of operando techniques to study additive manufacturing.

    View details for DOI 10.1107/S1600577525001675

    View details for PubMedID 40167485

  • X-ray induced grain boundary formation and grain rotation in Bi2Se3 SCRIPTA MATERIALIA Katagiri, K., Kozioziemski, B., Folsom, E., Goede, S., Wang, Y., Appel, K., Chalise, D., Cook, P. K., Eggert, J., Howard, M., Kim, S., Konopkova, Z., Makita, M., Nakatsutsumi, M., Nielsen, M. M., Pelka, A., Poulsen, H. F., Preston, T. R., Reddy, T., Schwinkendrof, J., Seiboth, F., Simons, H., Wang, B., Yang, W., Zastrau, U., Kim, H., Dresselhaus-Marais, L. E. 2025; 256

    View details for DOI 10.1016/j.scriptamat.2024.116416

    View details for Web of Science ID 001342787300001

  • Fatigue-based process window for laser beam powder bed fusion additive manufacturing INTERNATIONAL JOURNAL OF FATIGUE Reddy, T., Ngo, A., Miner, J. P., Gobert, C., Beuth, J. L., Rollett, A. D., Lewandowski, J. J., Narra, S. P. 2024; 187

    View details for DOI 10.1016/j.ijfatigue.2024.108428

    View details for Web of Science ID 001261972400001