Tharun Reddy

All Publications

• Ultrahigh flow strength in shocked nanopolycrystalline diamond. Science advances Hari, A., Katagiri, K., Li, W., Luccioni, D. P., Lin, R., Parsons, S. E., Xu, Z., Hari, R., Reddy, T., Cubit, E. W., Amouretti, A., Eggert, J. H., Inubushi, Y., Irifune, T., Irvine, S. J., Kodama, R., Koenig, M., Madril, L., Matsuoka, T., Miyanishi, K., Nakamura, H., Nishiyama, N., Okuchi, T., Ota, M., Sekine, T., Seto, Y., Shinmei, T., Sueda, K., Tange, Y., Takagi, S., Togashi, T., Umeda, Y., Wang, Y., Yabashi, M., Yabuuchi, T., Ozaki, N., Dresselhaus-Marais, L. E. 2026; 12 (38): eaed5546

  Abstract

  Extreme pressures and temperatures create conditions that allow even hard and brittle materials to flow plastically. Despite extensive research, the limits of flow strength under such conditions remain uncertain, and the mechanisms driving deformation at the relevant stresses are a subject of debate. Using femtosecond in situ x-ray diffraction experiments and large-scale molecular dynamics simulations, we demonstrate that stacking fault-mediated strengthening enables shock-compressed nanopolycrystalline diamond to achieve a peak flow strength of 92 ± 3 GPa at a stress of 212 ± 6 GPa. Our findings show that extreme conditions can unlock ultrahigh strength via a complex array of competing deformation mechanisms and thermodynamic effects.

  View details for DOI 10.1126/sciadv.aed5546

  View details for PubMedID 42758846

  View details for PubMedCentralID PMC13588184

• Shock-induced phase transitions and stacking fault formation in additively manufactured eutectic high-entropy alloy Ni40Co20Fe10Cr10Al18W2 SCRIPTA MATERIALIA Lin, R., Hari, A., Cubit, E. W., Katagiri, K., Parsons, S., Xu, Z., Ren, J., Yang, W., Amouretti, A., Irvine, S. J., Kodama, R., Madril, L., Miyanishi, K., Nakamura, H., Ozaki, N., Reddy, T., Seto, Y., Sueda, K., Togashi, T., Umeda, Y., Yabashi, M., Yabuuchi, T., Vohra, Y. K., Chen, W., Dresselhaus-Marais, L. E. 2026; 281

  View details for DOI 10.1016/j.scriptamat.2026.117347

  View details for Web of Science ID 001760205100001

• Phase Transitions of Eutectic High Entropy Alloy AlCoCrFeNi2.1 Under Shock Compression ADVANCED ENGINEERING MATERIALS Parsons, S., Katagiri, K., Chen, H., Hari, A., Cubit, E. W., Irvine, S., Luccioni, D., Lin, R., Madril, L., Reddy, T., McKinney, W. J., Ren, J., Yang, W., Ozaki, N., Amouretti, A., Kodama, R., Nakamura, H., Nakanishi, Y., Ota, M., Seto, Y., Takagi, S., Okuchi, T., Umeda, Y., Inubushi, Y., Miyanishi, K., Sueda, K., Togashi, T., Yabashi, M., Yabuuchi, T., Li, W., Specht, P., Cao, P., Chen, W., Vohra, Y. K., Dresselhaus-marais, L. 2026

  View details for DOI 10.1002/adem.202502073

  View details for Web of Science ID 001655626300001

• 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