Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session E7: Phase Transitions I |
Hide Abstracts |
Chair: Frank Cherne, Los Alamos National Laboratory Room: Regency Ballroom F |
Monday, July 10, 2017 3:30PM - 3:45PM |
E7.00001: Laser induced sub-nanosecond shock and ramp compression of Al and Zr Paulius Grivickas, Mike Armstrong, Jonathan Crowhurst, Harry Radousky, Joseph Zaug, Ryan Austin, Jon Belof Quasi-isentropic ramp waves generated by short laser pulses have been shown to have several advantages in studies of a material's EOS. An open question, however, remains; at what strain rates do the kinetics of material transformation become the limiting factor for such an approach? To address this question, we have subjected thin 0.2 -- 0.5 um films of Al and Zr to both shock and ramp wave compression using sub-nanosecond laser pulses. Velocimetry data was collected using an ultrafast interferometry with 10 ps resolution and analyzed using the Lagrangian method. The results obtained are compared to the corresponding Hugoniot and isentrope curves reported in the literature at longer time scales. In Al we discuss the dependence of the elastic precursor on the strain rate, while in Zr we focus on the changes relevant to the material's phase transitions. [Preview Abstract] |
Monday, July 10, 2017 3:45PM - 4:00PM |
E7.00002: Phase Transitions in Aluminum Under Shockless Compression at the Z Machine Jean-Paul Davis, Justin Brown, Luke Shulenburger, Marcus Knudson Aluminum 6061 alloy has been used extensively as an electrode material in shockless ramp-wave experiments at the Z Machine. Previous theoretical work suggests that the principal quasi-isentrope in aluminum should pass through two phase transitions at multi-megabar pressures, first from the ambient fcc phase to hcp at around 200 GPa, then to bcc at around 320 GPa. Previous static measurements in a diamond-anvil cell have detected the hcp phase above ~200 GPa along the room-temperature isentherm. Recent laser-based dynamic compression experiments have observed both the hcp and bcc phases using X-ray diffraction. Here we present high-accuracy velocity waveform data taken on pure and alloy aluminum materials at the Z Machine under shockless compression with ~200-ns rise-time to ~400 GPa using copper electrodes and lithium-fluoride windows. These are compared to recent EOS tables developed at Los Alamos National Laboratory, to our own results from diffusion quantum Monte-Carlo calculations, and to multi-phase EOS models with phase-transition kinetics. We find clear evidence of a fast transition around 200 GPa as expected, and a possible suggestion of a slower transition at higher pressure.\\ \\Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE AC04-94AL85000. [Preview Abstract] |
Monday, July 10, 2017 4:00PM - 4:15PM |
E7.00003: Application of the ab initio Z method to the melting of Al and Mg Shailesh Mehta Density functional theory based molecular dynamics has been used to investigate the accuracy of the Z method. The melt curve of Al is calculated to 3 Mbar and found to be in very good agreement with experiment. This is in contrast to a previous ab initio Z method calculation and an explanation is put forward to explain the failure of other work to achieve satisfactory agreement. Results will also be shown on work being performed to calculate the hcp-bcc-liquid triple point of Mg, by locating the intersection of the hcp and bcc melt curves. [Preview Abstract] |
Monday, July 10, 2017 4:15PM - 4:30PM |
E7.00004: The first observation of the bcc phase in aluminum compressed to 559 GPa Danae Polsin, Dayne Fratanduono, Ryan Rygg, Amy Jenei, Ray Smith, Jon Eggert, Michelle Gregor, Brian Henderson, Jacques Delettrez, Richard Kraus, Peter Celliers, Federica Coppari, Damian Swift, Chad McCoy, Christopher Seagle, Jean-Paul Davis, Stephen Burns, Thomas Boehly, Gilbert Collins Ramp compression is used to near isentropically compress aluminum samples to pressures up to 559 GPa and at temperatures below the melt. Nanosecond \textit{in-situ} x-ray diffraction is performed at the University of Rochester's Laboratory for Laser Energetics and the National Ignition Facility to directly measure the crystal structure at pressures where fcc--hcp and hcp--bcc phase transformations of Al exist. Velocimetry provided the pressure in the Al. The fcc--hcp and hpc--bcc transformations are confirmed experimentally at 243 GPa and 327 GPa, respectively. This is the first experimental evidence of the high-pressure bcc phase of Al. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944, the University of Rochester, and the New York State Energy Research and Development Authority. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700