<i>In situ</i> observation of phase transition in polycrystalline under high-pressure high-strain-rate shock compression by X-ray diffraction
Authors: Chen Xiao-Hui , Tan Bo-Zhong , Xue Tao , Ma Yun-Can , Jin Sai , Li Zhi-Jun , Xin Yue-Feng , Li Xiao-Ya , Li Jun ,   National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2021

The knowledge of phase transition of material under dynamic loading is an important area of research in inertial confinement fusion and material science. Though the shock-induced phase transitions of various materials over a broad pressure range have become a field of study for decades, the loading strain rates in most of these experiments is not more than <inline-formula><tex-math id="M2">\begin{document}$ {10^{6}}\;{{\rm{s}}^{ - 1}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20200929_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20200929_M2.png"/></alternatives></inline-formula>. However, in contrast with the strain rate range where the phase diagram is a good predictor of the crystal structure of a material, at higher strain rate (<inline-formula><tex-math id="M3">\begin{document}$ > {10^{6}}\;{{\rm{s}}^{ - 1}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20200929_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20200929_M3.png"/></alternatives></inline-formula>) the phase diagram measured can be quite different not only in shifting the boundary line between various phases, but also in giving a different sequence of crystal structure. High-power laser facility can drive shock wave and simultaneously provide a precisely synchronized ultra-short and ultra-intense X-ray source. Here, based on the Prototype laser facility, an <i>in situ</i> X-ray diffraction platform for diagnosing shock-induced phase transition of polycrystalline material is established. The <i>in situ</i> observation of material phase transition under high-strain-rate shock loading is carried out with typical metals of vanadium and iron. Diffraction results are consistent with vanadium remaining in the body-centered-cubic structure up to 69 GPa, while iron transforms from the body-centered-cubic structure into hexagonal-close-packed structure at 159 GPa. The compressive properties of vanadium and iron obtained in <i>in situ</i> X-ray diffraction experiment are in good agreement with their macroscopic Hugonoit curves. The decrease in the lattice volume over the pressure step period yields a strain rate on the order of <inline-formula><tex-math id="M4">\begin{document}$ {10^{8}} - {10^{9}}\;{{\rm{s}}^{ - 1}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20200929_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20200929_M4.png"/></alternatives></inline-formula>. The available of the presented <i>in situ</i> X-ray diffraction plateform offers the potential to extend our understanding of the kinetics of phase transition in polycrystalline under high-pressure high-strain-rate shock compression.