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Title: Shock-Driven Phase Transformations

Abstract

This presentation discusses the aspect of material science concerning the radiation of metals.

Authors:
 [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1338725
Report Number(s):
LA-UR-17-20051
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Jones, David Robert. Shock-Driven Phase Transformations. United States: N. p., 2017. Web. doi:10.2172/1338725.
Jones, David Robert. Shock-Driven Phase Transformations. United States. doi:10.2172/1338725.
Jones, David Robert. Thu . "Shock-Driven Phase Transformations". United States. doi:10.2172/1338725. https://www.osti.gov/servlets/purl/1338725.
@article{osti_1338725,
title = {Shock-Driven Phase Transformations},
author = {Jones, David Robert},
abstractNote = {This presentation discusses the aspect of material science concerning the radiation of metals.},
doi = {10.2172/1338725},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 05 00:00:00 EST 2017},
month = {Thu Jan 05 00:00:00 EST 2017}
}

Technical Report:

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  • Activities for this grant included: 1) Development of dynamic impact experiments to probe strength and phase transition influence on dynamic deformation, 2) development of modern strength and phase aware simulation capabilities, 3) and post-processing of experimental data with simulation and closed form analytical techniques. Two different dynamic experiments were developed to probe material strengths in solid metals (largely copper and iron in this effort). In the first experiment a flyer plate impacts a flat target with an opposite rippled surface that is partially supported by a weaker window material. Post mortem analysis of the target sample showed a strong andmore » repeatable residual plastic deformation dependence on grain orientation. Yield strengths for strain rates near 10 5 s -1 and plastic strains near ~50% were estimated to be around 180 to 240 MPa, varying in this range with grain orientation. Unfortunately dynamic real-time measurements were difficult with this setup due to diagnostic laser scattering; hence, an additional experimental setup was developed to complement these results. In the second set of experiments a rippled surface was ablated by a controlled laser pulsed, which launched a rippled shock front to an opposite initially flat diagnostic surface that was monitored in real-time with spatially resolved velocimetry techniques, e.g., line VISAR in addition to Transient Imaging Displacement Interferometry (TIDI) displacement measurements. This setup limited the displacements at the diagnostic surface to a reasonable level for TIDI measurements (~ less than one micrometer). These experiments coupled with analytical and numerical solutions provided evidence that viscous and elastic deviatoric strength affect shock front perturbation evolution in clearly different ways. Particularly, normalized shock front perturbation amplitudes evolve with viscosity (η) and perturbation wavelength (λ) as η/λ, such that increasing viscosity (or decreasing the initial wavelength) delays the perturbation decay. Conversely our experimental data, analysis and simulations show that for materials with elastic yield strength Y the normalized shock perturbation amplitude evolves with Yλ/A 0, which shows wavelength increases have the opposite effect as in viscous materials and perturbation decay is also dependent on initial amplitude A 0 (viscous materials are independent of this parameter). Materials where strength had clear strain rate dependence, e.g., such as a PTW material law, behaved similarly to materials with only an effective yield stress (elastic-perfectly plastic) in the shock front perturbation studies obeying a Y effλA 0 relationship where Y eff was a constant (near ~400 MPa for Cu for strain rates around 10 6 s -1). Magnitude changes in strain rate would increase Y eff as would be expected from the PTW behavior, but small perturbations (typical of regions behind the shock front) near a mean had little effect. Additional work based on simulations showed that phase transformation kinetics can affect the behavior of the perturbed shock front as well as the evolution of the RM-like instability that develops due to the imprint of the perturbed shock front on the initially flat surface as the shock breaks out.« less
  • EXAFS measurements of vanadium shocked to ~0.4 Mbar yield the compression and temperature in good agreement with hydrodynamic simulations and shock-speed measurements.
  • The high-temperature body-centered cubic γ phase in uranium alloys with approximately 10 at % titanium, niobium, zirconium, or molybdenum can be rendered metastable under critical cooling conditions; it may transform thence by a shear mechanism to form a characteristic banded structure or by a nucleation and growth process to equiaxed grains. These decomposition structures with differing metallographic appearances give similar x-ray patterns. The structures are designated ''distorted α '' since the patterns correspond to a contraction in the b-direction of the normal orthorhombic α cell.The formation of these metastable structures is apparently dependent upon composition, cooling rate, and the effectmore » of the solute element on the incubation period and decomposition rate of the metastable γ phase. (auth)« less