Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session Y01: Phase Transitions in MetalsRecordings Available
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Chair: Matthew Beason, Los Alamos National Laboratory Room: Anaheim Marriott Platinum 5 |
Friday, July 15, 2022 9:15AM - 9:30AM |
Y01.00001: Observable Second Order Ferromagnetic to Paramagnetic Phase Transformation in Magneto-Mechanically Coupled Galfenol under Shock Load Scott Turnage, Jonathan P Ligda, James U Cazamias, Cyril L Williams The strain and subsequent volumetric change resulting from magnetostriction has been shown to result in a second order ferromagnetic-to-paramagnetic phase transformation, but the effect has had negligible influence on the mechanical response of ferromagnetic materials placing the effect in the realm of interesting but impractical phenomena to exploit for strong shock mitigation. That is, until the recent development of highly magnetostrictive materials such as Galfenol. This work explores the shock and spall load response of Galfenol up to peak stresses of 24 GPa. The HEL and spall behavior measured by plate impact experimentation are reported; however, the most significant finding is the observation of a peak stress dependent cusp between the HEL and peak state. The cusp is observed to be dependent on a low applied magnetization suggesting it to be a second order ferromagnetic-to-paramagnetic phase transformation which, by way of strong magneto-mechanical coupling, results in a 3-wave structure within the velocity-time profiles. Interestingly, the Hugoniot elastic limit and spall strength do not seem noticeably influenced by the applied magnetization despite the never before seen magnetic response of the cusp. |
Friday, July 15, 2022 9:30AM - 9:45AM |
Y01.00002: Study of dynamic polymorphic phase transition in tin and its kinetics Eli Gudinetsky, Eugene B Zaretsky Previous studies of tin (Sn) dynamic phase diagram were focused on either shock or shockless loading of tin from its β-phase towards γ phase. Due to multiple techniques involved the β- γ phase boundary has been established based on substantially scattered points on pressure-temperature plane and is characterized by substantial uncertainty while the kinetics of the transition is not thoroughly understood yet. The goal of the present study was to accurately locate the dynamic β- γ boundary and to analyze the effect of initial sample state on kinetics of β- γ transition. This was done in several series of planar impact experiments with VISAR monitoring of the velocity of the rear surface of the samples of different thickness preheated up to temperatures varied from 300 K to Sn melting point. |
Friday, July 15, 2022 9:45AM - 10:00AM |
Y01.00003: Experimental and theoretical examination of shock-compressed copper through the fcc to bcc to melt phase transitions Melissa Sims, Richard J Briggs, Sebastien Hamel, Travis Volz, Federica Coppari, Martin G Gorman, Amy L Coleman, David J Erskine, Jon H Eggert, Raymond F Smith, June K Wicks Recent studies show a face-centered cubic (fcc) to body-centered cubic (bcc) transformation along the shock Hugoniot for several metals (i.e., Cu, Au, and Ag). In this study, we combine an experimental and theoretical approach to examine this transition. We completed laser-shock compression on Cu foils at nanosecond timescales with in situ X-ray diffraction (XRD) to examine the microstructural changes with stress. We study the changes within the fcc phase, the phase transition from fcc to bcc (pressures greater than 180 GPa), and the bcc phase. Textural analysis of the azimuthal intensities from the XRD images is consistent with transformation into the bcc phase through the Pitsch-distortion mechanism. We use embedded atom model molecular dynamics simulations to determine the stability of the bcc phase in pressure-temperature space. Our results indicate that the bcc phase is stabilized only at high-temperatures, and it remains stable at pressures greater than 500 GPa. |
Friday, July 15, 2022 10:00AM - 10:15AM |
Y01.00004: Shock Compression of Silver to 300 GPa: Solid State Transition, Melting, and Liquid State Response Maxwell K Wallace, Michael Winey, Yogendra M Gupta To gain insight into the shock compressed Ag states corresponding to the fcc-to-bcc transformation and melting observed using in-situ x-ray diffraction (XRD) measurements [PRL 124, 235701 (2020)], we measured wave profiles and longitudinal sound speeds in Ag at peak stresses ranging from 30 to 300 GPa. The measured Us-up results were fitted very well by a linear relationship over the entire stress range, providing an accurate determination of the Hugoniot curve. The measured sound speeds increased linearly with density compression to 171 GPa, showing that the sound speeds (and longitudinal moduli) in the fcc and bcc phases are very similar. Between 171 and 218 GPa, the sound speed dropped significantly, consistent with the melting reported using XRD measurements. From 218 to 300 GPa, the increasing sound speeds and Hugoniot states provide a determination of the liquid phase Ag response. Determination of the Grüneisen parameter (Γ) showed that Γ/V for liquid Ag is constant, but differs significantly from that for solid Ag at ambient conditions. Thus, the Mie- Grüneisen equation of state can be used to describe the Hugoniot and off-Hugoniot response of liquid Ag. |
Friday, July 15, 2022 10:15AM - 10:30AM |
Y01.00005: Shock-Ramp of SiO2 Melt Alisha N Clark, Steven D Jacobsen, Adam R Sarafian, Kyle R Cochrane, Joshua P Townsend, J Matthew D Lane, Jean-Paul Davis SiO2 is an endmember for all silicate materials. As such, having a robust equation of state for SiO2 is of fundamental importance for planetary and materials sciences. We will present experimental shock-ramp data from the Z-machine at Sandia National Laboratories for two samples of SiO2 melt at pressures >80 GPa. The starting materials are Corning SiO2 glasses: one sample is anhydrous containing <1ppm OH and the other is nominally hydrated with 1000ppm OH, typical of some industrially produced high-purity SiO2 glasses. Initial results suggest that the nominally hydrated SiO2 melt is stiffer on ramp compression than the anhydrous melt. Also, we find that the Los Alamos’ OpenSesame EOS SiO2 models the initial shock for both melts well, but does not to reproduce the ramp path for either sample. We will combine experimental data and theoretical results from classical atomistic simulation and density-functional theory calculations to investigate the atomic origin of the observed physical properties. |
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