Complex precipitation behavior in a Co-free high entropy alloy during aging

Matthew Luebbe; Fan Zhang; Jonathan D. Poplawsky; Jiaqi Duan; Haiming Wen

doi:10.1016/j.jallcom.2024.176384

Complex precipitation behavior in a Co-free high entropy alloy during aging

Matthew Luebbe, Fan Zhang, Jonathan D. Poplawsky, Jiaqi Duan, Haiming Wen

electron Microscopy and Microanalysis

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

High entropy alloys (HEAs) demonstrate high strength, thermal stability, and irradiation resistance, making them desirable for applications in nuclear reactors and other harsh environments. Many existing HEAs contain cobalt (Co), which makes them unsuitable for nuclear applications due to the long-term activation of Co. A previously studied Co-free alloy, (Fe_0.3Ni_0.3Mn_0.3Cr_0.1)₈₈Ti₄Al₈, exhibits high strength but compromised ductility due to its network of brittle precipitates upon aging. This work investigates the formation mechanism and evolution of the precipitates, including L1₂ (Ni₃Ti type, ordered face-centered cubic structure), B2 (NiAl type, ordered body-centered cubic structure), and Chi (FeCr-rich ordered α-Mn structure), in this alloy at 650 °C, the aging temperature that yields the alloy's peak strength after 120 hours. Using ex-situ scanning electron microscopy, transmission electron microscopy, and atom probe tomography, the precipitates were characterized in terms of their composition, morphology, and crystal structure at various aging times. In addition, synchrotron-based, in-situ X-ray diffraction was used to probe the evolution of precipitates in the bulk during key phases of in-situ aging. The L1₂ precipitates exhibit complex growth and coarsening behavior – their coarsening starts after just 24 hours, and competition between the L1₂ and B2 phases arises after 72 hours leading to a decrease in L1₂ volume fraction. Conversely, B2 and Chi precipitates exhibit delayed nucleation and growth, and do not form in observable quantities until after 24 hours. Once formed, however, these precipitates quickly dominate the microstructure, with >50 % volume fraction after 120 hours, leading to the previously observed mechanical properties. This study provides a foundational understanding of the evolution of multi-precipitate structures in HEAs and guides future alloy development and optimization by tailoring the precipitates.

Original language	English
Article number	176384
Journal	Journal of Alloys and Compounds
Volume	1007
DOIs	https://doi.org/10.1016/j.jallcom.2024.176384
State	Published - Dec 5 2024

Funding

This research was supported by the U.S. Nuclear Regulatory Commission Faculty Development Program (award number NRC 31310018M0044) and by U.S. National Science Foundation (award number DMR-2207965). Materials Research Center at Missouri University of Science and Technology is acknowledged for providing access to electron microscopes. Characterization using the JEM 2100 F was performed at the Center for Nanoscale Materials at Argonne National Laboratory under user proposal 75825, with Dr. Yuzi Liu coordinating the effort. This research used resources of the Advanced Photon Source and the Center for Nanoscale Materials, U.S. Department of Energy (DOE) Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank James Burns for assistance in performing APT sample preparation and running the APT experiments. This research was supported by the U.S. Nuclear Regulatory Commission Faculty Development Program (award number NRC 31310018M0044) and by U.S. National Science Foundation (award number DMR-2207965). Materials Research Center at Missouri University of Science and Technology is acknowledged for providing access to electron microscopes. Characterization using the JEM 2100 F was performed at the Center for Nanoscale Materials at Argonne National Laboratory under user proposal 75825, with Dr. Yuzi Liu coordinating the effort. This research used resources of the Advanced Photon Source and the Center for Nanoscale Materials, U.S. Department of Energy (DOE) Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank James Burns for assistance in performing APT sample preparation and running the APT experiments.

Keywords

High-entropy alloy
Kinetics
Microstructure
Precipitation evolution
Precipitation strengthening

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10.1016/j.jallcom.2024.176384

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title = "Complex precipitation behavior in a Co-free high entropy alloy during aging",

abstract = "High entropy alloys (HEAs) demonstrate high strength, thermal stability, and irradiation resistance, making them desirable for applications in nuclear reactors and other harsh environments. Many existing HEAs contain cobalt (Co), which makes them unsuitable for nuclear applications due to the long-term activation of Co. A previously studied Co-free alloy, (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8, exhibits high strength but compromised ductility due to its network of brittle precipitates upon aging. This work investigates the formation mechanism and evolution of the precipitates, including L12 (Ni3Ti type, ordered face-centered cubic structure), B2 (NiAl type, ordered body-centered cubic structure), and Chi (FeCr-rich ordered α-Mn structure), in this alloy at 650 °C, the aging temperature that yields the alloy's peak strength after 120 hours. Using ex-situ scanning electron microscopy, transmission electron microscopy, and atom probe tomography, the precipitates were characterized in terms of their composition, morphology, and crystal structure at various aging times. In addition, synchrotron-based, in-situ X-ray diffraction was used to probe the evolution of precipitates in the bulk during key phases of in-situ aging. The L12 precipitates exhibit complex growth and coarsening behavior – their coarsening starts after just 24 hours, and competition between the L12 and B2 phases arises after 72 hours leading to a decrease in L12 volume fraction. Conversely, B2 and Chi precipitates exhibit delayed nucleation and growth, and do not form in observable quantities until after 24 hours. Once formed, however, these precipitates quickly dominate the microstructure, with >50 \% volume fraction after 120 hours, leading to the previously observed mechanical properties. This study provides a foundational understanding of the evolution of multi-precipitate structures in HEAs and guides future alloy development and optimization by tailoring the precipitates.",

keywords = "High-entropy alloy, Kinetics, Microstructure, Precipitation evolution, Precipitation strengthening",

author = "Matthew Luebbe and Fan Zhang and Poplawsky, \{Jonathan D.\} and Jiaqi Duan and Haiming Wen",

note = "Publisher Copyright: {\textcopyright} 2024 Elsevier B.V.",

year = "2024",

month = dec,

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doi = "10.1016/j.jallcom.2024.176384",

language = "English",

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journal = "Journal of Alloys and Compounds",

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TY - JOUR

T1 - Complex precipitation behavior in a Co-free high entropy alloy during aging

AU - Luebbe, Matthew

AU - Zhang, Fan

AU - Poplawsky, Jonathan D.

AU - Duan, Jiaqi

AU - Wen, Haiming

PY - 2024/12/5

Y1 - 2024/12/5

N2 - High entropy alloys (HEAs) demonstrate high strength, thermal stability, and irradiation resistance, making them desirable for applications in nuclear reactors and other harsh environments. Many existing HEAs contain cobalt (Co), which makes them unsuitable for nuclear applications due to the long-term activation of Co. A previously studied Co-free alloy, (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8, exhibits high strength but compromised ductility due to its network of brittle precipitates upon aging. This work investigates the formation mechanism and evolution of the precipitates, including L12 (Ni3Ti type, ordered face-centered cubic structure), B2 (NiAl type, ordered body-centered cubic structure), and Chi (FeCr-rich ordered α-Mn structure), in this alloy at 650 °C, the aging temperature that yields the alloy's peak strength after 120 hours. Using ex-situ scanning electron microscopy, transmission electron microscopy, and atom probe tomography, the precipitates were characterized in terms of their composition, morphology, and crystal structure at various aging times. In addition, synchrotron-based, in-situ X-ray diffraction was used to probe the evolution of precipitates in the bulk during key phases of in-situ aging. The L12 precipitates exhibit complex growth and coarsening behavior – their coarsening starts after just 24 hours, and competition between the L12 and B2 phases arises after 72 hours leading to a decrease in L12 volume fraction. Conversely, B2 and Chi precipitates exhibit delayed nucleation and growth, and do not form in observable quantities until after 24 hours. Once formed, however, these precipitates quickly dominate the microstructure, with >50 % volume fraction after 120 hours, leading to the previously observed mechanical properties. This study provides a foundational understanding of the evolution of multi-precipitate structures in HEAs and guides future alloy development and optimization by tailoring the precipitates.

AB - High entropy alloys (HEAs) demonstrate high strength, thermal stability, and irradiation resistance, making them desirable for applications in nuclear reactors and other harsh environments. Many existing HEAs contain cobalt (Co), which makes them unsuitable for nuclear applications due to the long-term activation of Co. A previously studied Co-free alloy, (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8, exhibits high strength but compromised ductility due to its network of brittle precipitates upon aging. This work investigates the formation mechanism and evolution of the precipitates, including L12 (Ni3Ti type, ordered face-centered cubic structure), B2 (NiAl type, ordered body-centered cubic structure), and Chi (FeCr-rich ordered α-Mn structure), in this alloy at 650 °C, the aging temperature that yields the alloy's peak strength after 120 hours. Using ex-situ scanning electron microscopy, transmission electron microscopy, and atom probe tomography, the precipitates were characterized in terms of their composition, morphology, and crystal structure at various aging times. In addition, synchrotron-based, in-situ X-ray diffraction was used to probe the evolution of precipitates in the bulk during key phases of in-situ aging. The L12 precipitates exhibit complex growth and coarsening behavior – their coarsening starts after just 24 hours, and competition between the L12 and B2 phases arises after 72 hours leading to a decrease in L12 volume fraction. Conversely, B2 and Chi precipitates exhibit delayed nucleation and growth, and do not form in observable quantities until after 24 hours. Once formed, however, these precipitates quickly dominate the microstructure, with >50 % volume fraction after 120 hours, leading to the previously observed mechanical properties. This study provides a foundational understanding of the evolution of multi-precipitate structures in HEAs and guides future alloy development and optimization by tailoring the precipitates.

KW - High-entropy alloy

KW - Kinetics

KW - Microstructure

KW - Precipitation evolution

KW - Precipitation strengthening

UR - https://www.scopus.com/pages/publications/85203458631

U2 - 10.1016/j.jallcom.2024.176384

DO - 10.1016/j.jallcom.2024.176384

M3 - Article

AN - SCOPUS:85203458631

SN - 0925-8388

VL - 1007

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

M1 - 176384

ER -

Complex precipitation behavior in a Co-free high entropy alloy during aging

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