Phase stability of a eutectic high entropy alloy under extremes of pressures and temperatures

Journal Article · Tue Feb 20 00:00:00 EST 2024 · AIP Advances

DOI:https://doi.org/10.1063/5.0188644· OSTI ID:2309688

Pope, Andrew D.  ^[1]; Iwan, Seth  ^[1]; Clay, Matthew P.  ^[1]; Ren, Jie  ^[2]; Yang, Wuxian  ^[2]; Chen, Wen  ^[2]; Vohra, Yogesh K.  ^[1]

---

1. Univ. of Alabama, Birmingham, AL (United States)
2. Univ. of Massachusetts, Amherst, MA (United States)

Additively manufactured high-entropy alloys are of interest because of their unique combination of high yield strength and large ductility achieved with far-from-equilibrium crystalline phases and micro/nanostructure morphology. We report on the phase transformation and thermal equation of state of the eutectic high-entropy alloy (EHEA) Al₁₈Co₂₀Cr₁₀Fe₁₀Ni₄₀W₂, produced by laser powder-bed fusion (L-PBF). The EHEA was studied in a large-volume Paris–Edinburgh cell using energy-dispersive x-ray diffraction to a pressure of 5.5 GPa and a temperature of 1723 K. Static compression studies in diamond anvil cells using angle-dispersive x-ray diffraction extended the high-pressure structural data to 317 GPa at ambient temperature. The initial dual-phase nanolamellar face-centered cubic (FCC) and body-centered cubic (BCC) structure of Al₁₈Co₂₀Cr₁₀Fe₁₀Ni₄₀W₂ transforms into a single FCC phase under high pressure, with the BCC-to-FCC phase transformation completing at 9 ± 2 GPa. The FCC phase remained stable up to the highest pressure of 317 GPa. The measured thermal equation of state for the FCC phase of Al₁₈Co₂₀Cr₁₀Fe₁₀Ni₄₀W₂ is presented up to 5.5 GPa and 1473 K. We observed melting of the EHEA at 1698 ± 25 K at a pressure of 5.5 GPa, and the recrystallized sample shows an increased fraction of the CsCl-type (B2) phase at ambient conditions following release from the high-pressure high-temperature state. The BCC-to-FCC phase transition completion pressure is correlated with the nanolamellae thickness of the BCC layer in this diffusion-less transformation at ambient temperature.

• Research Organization: Univ. of Alabama, Birmingham, AL (United States); Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0004154; AC02-06CH11357
• OSTI ID: 2309688
• Journal Information: AIP Advances, Vol. 14, Issue 2; ISSN 2158-3226
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
extreme conditions
high-entropy alloys
additive manufacturing
phase transitions
thermal equation of state