Rules for crystallite size and dislocation density evolution in phases during pressure and plastic strain-induced α-ω transformation in Zr

POSTER

Abstract

The first in-situ XRD studies of the crystallite size and dislocation density evolution in phases during α-ω phase transformation (PT) in Zr under hydrostatic loading and plastic flow are performed. Rough diamond anvils (rough-DA) are introduced to intensify all occurring processes during plastic compression of Zr in a diamond anvil cell (DAC). The main rule is found that during α-ω PT, the crystallite size and dislocation density in ω-Zr depend solely on the volume fraction of ω-Zr and are independent of pressure, plastic strain tensor, its path, and initial nanostructure. Crystallite size in ω-Zr increases from 10 to 60 nm during the PT. Rough-DA produce a steady nanostructure in α-Zr before PT with smaller crystallite size and larger dislocation density than smooth-DA, leading to a reduction of the minimum PT pressure to a record value of 0.67 GPa, 9 times smaller than under hydrostatic loading. Under hydrostatic loading, the microstructure significantly varies before, during, and after PT, differently during loading and unloading. During the PT, microstructural parameters in ω-Zr are functions of the volume fraction of ω Zr only, independent of the plastic straining before transformation and pressure. The results may bring up economic strategies for producing nanocomposites and single-phase nanostructured materials with optimal properties.

*Support from NSF (DMR-2246991), ARO (W911NF2420145), and DOE (DE-AC02-06CH11357) is appreciated.

Publication: 1. Pandey K. K. and Levitas V. I. In situ quantitative study of plastic strain-induced phase transformations under high pressure: Example for ultra-pure Zr. Acta Materialia, 2020, 196, 338-346.
2. Lin F., Levitas V.I., Pandey K.K., Yesudhas S., Park C. In-situ study of rules of nanostructure evolution, severe plastic deformations, and friction under high pressure. Materials Research Letters, 2023, 11, 757-763.
3. Levitas V.I. Recent in situ Experimental and Theoretical Advances in Severe Plastic Deformations, Strain-Induced Phase Transformations, and Microstructure Evolution under High Pressure. Material Transactions, 64, 1866-1878 (2023).
4. Lin F., Levitas V.I., Pandey K., Yesudhas S., Park C. (2025) Rules for the Crystallite Size and Dislocation Density Evolution in Phases During α-ω Transformation in Zr Under High-Pressure and Severe Plastic Flow. SSRN: http://dx.doi.org/10.2139/ssrn.5118109.
5. Pandey K.K., Levitas V.I., Park C., and Shen G. In situ study of microstructure evolution and α-ω phase transition in annealed and pre-deformed Zr under hydrostatic loading. Journal of Applied Physics, 2024, 136, 115901.
6. Lin F., Levitas V.I., Pandey K., Yesudhas S., Park C. (2025) Rules for the Crystallite Size and Dislocation Density Evolution in Phases During α-ω Transformation in Zr Under High-Pressure and Severe Plastic Flow. SSRN: http://dx.doi.org/10.2139/ssrn.5118109.

Presenters

  • Sorb Yesudhas

    • Iowa State University

Authors

  • Feng Lin

    • Iowa State University

  • Krishan K Pandey

    • High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
    • Bhabha Atomic Research Center

  • Valery I. Levitas

    • Iowa State University

  • Sorb Yesudhas

    • Iowa State University

  • Changyong Park

    • Argonne National Laboratory
    • HPCAT, X-ray Science Division, Argonne National Laboratory
    • HPCAT, X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA