Equation of state of additively manufactured eutectic high entropy alloy up to 302 GPa*

High entropy alloys (HEAs) are an attractive class of material, with many HEAs having superior mechanical properties compared to traditional alloys. We report an angle dispersive x-ray diffraction experiment of the eutectic dual-phase [face-centered cubic (FCC) and body-centered cubic (BCC)] HEA AlCoCrFeNi_2.1, which consists of alternating lamellae of FCC and BCC microstructures (Ren, J. et al. Nature 608, 62–68, 2022). Using a diamond anvil cell at ambient temperature at the Advanced Photon Source (HPCAT), we achieve a peak pressure of 302 GPa, as measured with a tungsten pressure marker. While the BCC phase irreversibly transforms by a pressure of 21±3 GPa (Pope, A. D. et al. AIP Adv., submitted), the FCC phase is stable throughout. The resulting pressure-volume isotherm for the FCC phase is well-described by a third-order Birch-Murnaghan equation of state with V₀ = 11.528 ų/atom, K₀ = 190 GPa and K₀' = 4.07.