TU Darmstadt / ULB / TUbiblio

Grain boundary segregation induced precipitation in a non equiatomic nanocrystalline CoCuFeMnNi compositionally complex alloy

Mantha, Lakshmi Sravani ; MacDonald, Benjamin E. ; Mu, Xiaoke ; Mazilkin, Andrey ; Ivanisenko, Julia ; Hahn, Horst ; Lavernia, E. J. ; Katnagallu, Shyam ; Kübel, Christian (2021)
Grain boundary segregation induced precipitation in a non equiatomic nanocrystalline CoCuFeMnNi compositionally complex alloy.
In: Acta Materialia, 220
doi: 10.1016/j.actamat.2021.117281
Article, Bibliographie

Abstract

Compositionally complex alloys (CCAs) in a nanocrystalline state often involve complex and poorly understood phase transformations which can consequently result in grain growth even at low temperatures. A detailed study of the microstructure and phase stability in CCAs is challenging due to the presence of multiple principal components. In view of these challenges the objective of the present study is to establish a systematic understanding of the phase evolution in a face centered cubic non equiatomic nanocrystalline CCA (CoCuFeMnNi). To accomplish this objective, we employed in-situ transmission electron microscope heating in combination with automated crystal orientation mapping (ACOM) and energy filtered transmission electron microscopy (EFTEM) to elucidate the sequence of phase decomposition of the high-pressure torsion (HPT) processed CoCuFeMnNi. Our analysis reveals a complex succession of grain boundary segregation and depletion steps leading to the formation of a FeCo-rich secondary phase. Our results show that prior to the formation of the secondary phase, Cu, Ni and Co segregate and Fe and Mn deplete at the grain boundaries. After the FeCo precipitation is triggered, Mn segregates to the grain boundaries along with Ni and Cu, whereas Fe and Co are depleted. The FeCo precipitates have a B2 crystal structure and typically exhibit a Kurdjumov-Sachs (K-S) and/or Nishyama-Wasserman (N-W) orientation relationships with adjacent fcc grains. Ex-situ heat treated CoCuFeMnNi analyzed by atom probe tomography (APT) revealed a highly heterogeneous segregation of the different elements to different grain boundaries. The FeCo-rich precipitates contain trace amounts of Ni, whereas Cu is rejected leading to the formation of a separate Cu rich phase. This complex segregation phenomenon is assisted by the high fraction of grain boundaries and triple junctions in the nanocrystalline material, which are critical for the phase evolution in this alloy, which is not frequently observed in the corresponding coarse-grained material. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Item Type: Article
Erschienen: 2021
Creators: Mantha, Lakshmi Sravani ; MacDonald, Benjamin E. ; Mu, Xiaoke ; Mazilkin, Andrey ; Ivanisenko, Julia ; Hahn, Horst ; Lavernia, E. J. ; Katnagallu, Shyam ; Kübel, Christian
Type of entry: Bibliographie
Title: Grain boundary segregation induced precipitation in a non equiatomic nanocrystalline CoCuFeMnNi compositionally complex alloy
Language: English
Date: November 2021
Publisher: Elsevier
Journal or Publication Title: Acta Materialia
Volume of the journal: 220
DOI: 10.1016/j.actamat.2021.117281
Abstract:

Compositionally complex alloys (CCAs) in a nanocrystalline state often involve complex and poorly understood phase transformations which can consequently result in grain growth even at low temperatures. A detailed study of the microstructure and phase stability in CCAs is challenging due to the presence of multiple principal components. In view of these challenges the objective of the present study is to establish a systematic understanding of the phase evolution in a face centered cubic non equiatomic nanocrystalline CCA (CoCuFeMnNi). To accomplish this objective, we employed in-situ transmission electron microscope heating in combination with automated crystal orientation mapping (ACOM) and energy filtered transmission electron microscopy (EFTEM) to elucidate the sequence of phase decomposition of the high-pressure torsion (HPT) processed CoCuFeMnNi. Our analysis reveals a complex succession of grain boundary segregation and depletion steps leading to the formation of a FeCo-rich secondary phase. Our results show that prior to the formation of the secondary phase, Cu, Ni and Co segregate and Fe and Mn deplete at the grain boundaries. After the FeCo precipitation is triggered, Mn segregates to the grain boundaries along with Ni and Cu, whereas Fe and Co are depleted. The FeCo precipitates have a B2 crystal structure and typically exhibit a Kurdjumov-Sachs (K-S) and/or Nishyama-Wasserman (N-W) orientation relationships with adjacent fcc grains. Ex-situ heat treated CoCuFeMnNi analyzed by atom probe tomography (APT) revealed a highly heterogeneous segregation of the different elements to different grain boundaries. The FeCo-rich precipitates contain trace amounts of Ni, whereas Cu is rejected leading to the formation of a separate Cu rich phase. This complex segregation phenomenon is assisted by the high fraction of grain boundaries and triple junctions in the nanocrystalline material, which are critical for the phase evolution in this alloy, which is not frequently observed in the corresponding coarse-grained material. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Uncontrolled Keywords: nanocrystalline structure, in-situ TEM, grain boundary segregation-induced phase transformation, atom probe tomography (APT), high-pressure torsion (HPT)
Identification Number: Artikel-ID: 117281
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > In-situ electron microscopy
Date Deposited: 12 Jun 2024 08:31
Last Modified: 12 Jun 2024 08:31
PPN:
Export:
Suche nach Titel in: TUfind oder in Google
Send an inquiry Send an inquiry

Options (only for editors)
Show editorial Details Show editorial Details