Dynamic probing of the high pressure and temperature phase transitions of iron on millisecond timescales

We investigate the high pressure (HP) and high temperature (HT) phase transitions of iron using the fast-loading dynamic-diamond anvil cell (d-DAC) setup at the 13-ID-D beamline at Advanced Photon Source in Argonne National Laboratory. Using the d-DAC apparatus, we demonstrate compression rates of over 1 TPa/s, coupled with doubled sided laser heating and in-situ x-ray diffraction with millisecond time resolution. Iron HP-HT phase transitions have been studied extensively in quasi-static DAC and multi-anvil cell experiments [1-3]. Crucially, the γ→ɛ phase transition (i.e., fcc to hcp) of iron has yet to be explored dynamically; indeed, conventional shock-compression experiments, e.g., laser ablation and gas gun [4-5], are constrained along the Hugoniot curve in P-T space and cannot access the γ phase upon compression [5]. Here, we demonstrate a novel approach that allows us to dynamically probe HP-HT phase transitions in vast region of P-T space and in off-Hugoniot states, providing the first insight on the γ→ɛ transition of iron over fast (ms) compression timescales.

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[4] Branch, B. and B. J. Jensen, AIP Conference Proceedings, 1979(1), (2018)

[5] Hawreliak, J. A. and S. J. Turneaure, Journal of applied physics, 129(13), 135901 (2021)