FYI [https://urldefense.us/v3/__https://info.aps.org/l/640833/2022-10-27/27md6z/6... ] [https://urldefense.us/v3/__https://info.aps.org/l/640833/2023-09-20/2q6ypd/6... ] Dear Colleagues, Due to technical difficulties on the original date, this seminar has been rescheduled to March 6. Please join us for a APS Topical Group on Compression of Condensed Matter (GCCM) virtual seminar. Information on the seminar and how to join are below. We would also like to solicit nominations for future seminars and anticipate having a mix of a single speaker or two speakers during an hour time slot. Please email your nominations to Tracy Vogler (tjvogle@sandia.govmailto:tjvogle@sandia.gov). GCCM Virtual Seminar Series Organizing Committee Kaleb Burrage, Harrison Horn, Pat Kalita, Tom Lockard, Afreen Syeda, Nenad Velisavljevic, Tracy Vogler, and Yanyao Zhang New Rules of Coupled Severe Plastic Deformations, Phase Transformations, and Microstructure Evolution under High Pressure Professor Valery I. Levitas Departments of Aerospace and Mechanical Engineering Iowa State University Date: Thursday, March 6, 2025 at 12 p.m. ET / 9 a.m. PT Preregister and Receive Zoom<https://urldefense.us/v3/__https://info.aps.org/e/640833/sBTKqoEXqF--1JVQ--r... > Abstract Plastic strain-induced phase transformations (PTs) during compression in diamond anvil cell (DAC) and torsion in rotational DAC (RDAC) require entirely different thermodynamic and kinetic treatments and experimental characterization [1,2] than pressure-induced PTs. The four-scale theory for plastic strain-induced PTs is developed [1], including molecular dynamics and first-principle simulations, developed nanoscale and scale-free phase-field approaches, and the behavior of the sample in DAC/RDAC at the macroscale. Various experimental effects are reproduced and predicted. It became clear [2-4] that their description strongly depends on the microstructure and its evolution, and microstructure evolves during strain-induced PTs. Four topics will be covered. 1. It was found [3,4] for severely predeformed Zr that (a) crystallite size and dislocation density in both phases in a single-phase state, the minimum pressure for the strain-induced α-ω PT in Zr, and the pressure-dependent yield strength of ω-Zr are getting steady and independent of plastic strain tensor and strain path ; (b) crystallite size and dislocation density in ω-Zr and (with some outliners) α-Zr during PT are independent of pressure, plastic strain tensor, and its path, and depend on the volume fraction of the high-pressure phase only. Obtained results can be used to find economic ways of grain refinement during PT and obtain nanocomposite with optimal properties. 2. Coupled experimental-analytical-computational approaches, utilizing synchrotron X-ray diffraction, are developed [5,6] to solve an inverse problem and find fields of all components of stress and plastic strain tensors and friction rules before, during, and after α-ω PT in strongly plastically predeformed Zr. In addition, the kinetics of strain-induced PT is described in the whole sample. 3. We revealed in situ various unexpected plastic strain-induced PT phenomena in Si [7]. Thus, for 100 nm Si, strain-induced PT Si-I→Si-II initiates at 0.3 GPa versus 16.2 GPa under hydrostatic conditions; for 30 nm Si, it is 6.1 GPa versus ∞ since it does not occur. For 100 nm Si-I→Si-III, it is 0.6 GPa vs. ∞. The predicted theoretical correlation between the direct and inverse Hall-Petch effect of the grain size on the yield strength and the minimum pressure for strain-induced PT is confirmed. Retaining Si-II at ambient pressure and obtaining reverse Si-II→Si-I PT are achieved for the first time. Retaining single-phase Si III is achieved at much more economic conditions than the currently known. 4. A new theory is developed for the plastic strain-induced olivine-spinel PT in a shear band, which resolves multiple existing puzzles in the mechanism of deep-focus earthquakes [8]. Conceptual experimental confirmation is obtained [9]. The obtained results offer a new fundamental understanding of strain-induced PTs under high pressure in DAC/RDAC. They create new opportunities in material design, synthesis, and processing of nanostructured materials by severe plastic deformations at low pressure, methods of controlling PTs and nanostructures, and searching for new high-pressure phases and phenomena. 1. Levitas V.I. Material Transactions, 60, 1294-1301 (2019). 2. Levitas V.I. Material Transactions, 64, 1866-1878 (2023). 3. Lin F., Levitas V.I., Pandey K.K., Yesudhas S., Park C. Materials Research Letters, 2023, 11, 757-763. 4. Lin F., Levitas V.I., Pandey K., Yesudhas S., Park C. (2023) https://urldefense.us/v3/__https://info.aps.org/e/640833/10-48550-arXiv-2305... 5. Levitas V.I., Dhar A., and Pandey K.K. Nature Communication, 14, 5955 (2023). 6. Dhar A., Levitas V.I., Pandey K. K., Park C., Somayazulu M., Velisavljevic N. Nature NPJ Computational Materials, 10, 290 (2024). 7. Yesudhas S., Levitas V.I., Lin F., Pandey K. K., Smith J. Nature Communications, 15, 7054 (2024). 8. Levitas V.I. Nature Communications, 13, 6291 (2022). 9. Lin F., Levitas V.I., Yesudhas S., and J. Smith. (2023) https://urldefense.us/v3/__https://info.aps.org/e/640833/10-48550-arXiv-2305... Geophysical Research Letters, 2025, DOI: 10. 1029/2024GL111281. Biography Professor Valery Levitas, Iowa State University Valery I. Levitas is an Anson Marston Distinguished Professor in Engineering and Murray Harpole Chair in Engineering at Iowa State University, Departments of Aerospace and Mechanical Engineering, Ames, IA, USA. He received his PhD and then worked as a group leader and Leading Researcher at the Institute for Superhard Materials of the Ukrainian Academy of Sciences, Kyiv. Later, he worked at the University of Hannover, Germany, Texas Tech University, and Iowa State University. He brought a unique device, the rotational diamond anvil cell (RDAC) to the USA from his former group in Kyiv. Valery initiated (a) in situ experimental studies of coupled severe plastic deformations, plastic strain-induced phase transformations, and microstructure evolution under high pressure with RDAC, (b) corresponding four-scale theory (from atomistic to macroscale), and (c) coupled experimental-computational methods to extract information about all heterogeneous fields in the sample, mechanical and transformational properties, as well as governing rules and new phenomena. He published 485 scientific papers, including 302 refereed journal papers, 3 monographs, 11 book chapters, as well as 11 patents; he has >14,000 citations and an h-factor of 70. Valery presented numerous plenary, keynote, and invited lectures for high pressure, nanomaterials by severe plastic deformations, mechanochemistry, phase transformations, material science, and mechanics of materials communities. He received various national and international honors and awards, including membership in the EU Academy of Sciences and the European Academy of Sciences and Arts. Join the conversation! Visit your unit's website<https://urldefense.us/v3/__https://info.aps.org/e/640833/membership-communit... > and log in to your unit's APS Engage discussion community. Ask for career advice, support or mentor members, learn about or share opportunities (e.g. meetings and funding opportunities), and more. 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