Dynamic reflectance changes in high-purity zirconium when it is shocked from the α to ω phase
[1];
[2];
[3];
- Nevada National Security Site, Santa Barbara, CA (United States). Special Technologies Lab.
- Nevada National Security Site, Los Alamos, NM (United States). New Mexico Operations
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Nevada National Security Site, Santa Barbara, CA (United States). Special Technologies Lab.; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Flash lamp-illuminated integrating spheres have been used to measure the dynamic reflectance at the interface between a shocked metal target and a window maintaining the shock stress. In conjunction with radiance measurements, this method was recently used to study the pressure versus temperature phase boundary of the beta phase to body-centered-tetragonal transition of tin at around 13 GPa and, in separate experiments, to show a relationship between the reflectance and the phase fraction. We have used this technique to measure the ratio, R, of the dynamic reflectance relative to the ambient value for a high-purity zirconium sample attached to a sapphire window to study the alpha to omega phase transition. Nine experiments cover the range of stress, σ, from 4 to 16 GPa at six wavelengths from 500 to 1550 nm. The two phases in zirconium differ in volume by <1%, so a phase change between them can be difficult to identify from anomalies in the particle velocity measured on the shock Hugoniot. The phase boundary is believed to cross the Hugoniot around 3 GPa, but dynamically it is observed at much higher stresses >6 GPa. Our results show that the relative reflectance decreases upon initial shock in the alpha state but increases as the material transforms to its omega state. The slope dR/dσ changes the sign around the phase transition. For shocks below 6 GPa, dR/dσ < 0, and for σ above 10 GPa, dR/dσ > 0. In the stress region between 6 and 10 GPa, dR/dσ varies somewhat, perhaps due to the band structure or because the transition is incomplete there. I. INTRODUCTION
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1492673
- Report Number(s):
- LA-UR-18-28548
- Journal Information:
- Journal of Applied Physics, Vol. 124, Issue 18; ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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