TY - JOUR

T1 - Short-range chemical order and local lattice distortion in a compositionally complex alloy

AU - Fantin, Andrea

AU - Lepore, Giovanni Orazio

AU - Manzoni, Anna M.

AU - Kasatikov, Sergey

AU - Scherb, Tobias

AU - Huthwelker, Thomas

AU - d'Acapito, Francesco

AU - Schumacher, Gerhard

N1 - Funding Information: We acknowledge the Paul Scherrer Institut, Villigen, Switzerland and the CNR-IOM-OGG at ESRF for provision of beamtime at PHOENIX and LISA-BM08 beamlines, respectively and we would like to thank the beamline staff for assistance during the experiments. LISA is a project (DFM.AD006.072) funded by the Consiglio Nazionale delle Richerche. C.Leistner and C. Förster (HZB) are acknowledged for help in sample preparation, and J. Nissen from Technische Universität Berlin for carrying out the EPMA measurements. We thank S. Dramé for preparing and performing the ATP measurements. A. Minelli (Department of Chemistry, University of Oxford) is kindly acknowledged for the enlightening discussions. The authors are grateful to the German Research Foundation (DFG) for the financial support by BA 1170/39-1 through the Priority Programme SPP 2006 “Compositionally Complex Alloys - High Entropy Alloys (CCA - HEA)”, and to the German-Russian Interdisciplinary Science Center (G-RISC), by P-2018b-11 funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD). Publisher Copyright: © 2020 Acta Materialia Inc. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/7

Y1 - 2020/7

N2 - This work presents an X-ray absorption spectroscopy study on a single-phase state of the Al8Cr17Co17Cu8Fe17Ni33 compositionally complex alloy, focused on the local crystal structure around each alloying element. The comparison of 1st shell bond lengths, obtained by the analysis of extended X-ray absorption fine structure (EXAFS) measured at the K-edges of each alloying element, indicates that Al8Cr17Co17Cu8Fe17Ni33 crystallizes in a distorted arrangement of an fcc lattice. A modest bond length dependence of the alloying elements with increasing atomic number is observed, with minima and maxima at Cr/Co, and Al/Cu, respectively. 1st shell bond lengths spread over ~0.03 Å; consequently, such variations cannot result in lattice distortions greater than ~0.04 Å. EXAFS results clearly indicate short-range order in the alloy: pairing of Al with Ni and Cu is favored, correlating well with a γ’ precipitate composition (Al-Ni-Cu rich) reported in previous work, while Al-Cr bonding is unfavored and no Al-Al pairs are observed. Electronic structure information was obtained through comparison between near-edge regions of alloying elements and corresponding pure metals. Intensity comparison of K-edge features agree with a charge variation of p states in Al8Cr17Co17Cu8Fe17Ni33, where Ni and Cu act as p states electron acceptors, suggesting an orbital hybridization with Al, responsible for a shrinkage in Al metallic radius in the alloy by ∼0.17 Å.

AB - This work presents an X-ray absorption spectroscopy study on a single-phase state of the Al8Cr17Co17Cu8Fe17Ni33 compositionally complex alloy, focused on the local crystal structure around each alloying element. The comparison of 1st shell bond lengths, obtained by the analysis of extended X-ray absorption fine structure (EXAFS) measured at the K-edges of each alloying element, indicates that Al8Cr17Co17Cu8Fe17Ni33 crystallizes in a distorted arrangement of an fcc lattice. A modest bond length dependence of the alloying elements with increasing atomic number is observed, with minima and maxima at Cr/Co, and Al/Cu, respectively. 1st shell bond lengths spread over ~0.03 Å; consequently, such variations cannot result in lattice distortions greater than ~0.04 Å. EXAFS results clearly indicate short-range order in the alloy: pairing of Al with Ni and Cu is favored, correlating well with a γ’ precipitate composition (Al-Ni-Cu rich) reported in previous work, while Al-Cr bonding is unfavored and no Al-Al pairs are observed. Electronic structure information was obtained through comparison between near-edge regions of alloying elements and corresponding pure metals. Intensity comparison of K-edge features agree with a charge variation of p states in Al8Cr17Co17Cu8Fe17Ni33, where Ni and Cu act as p states electron acceptors, suggesting an orbital hybridization with Al, responsible for a shrinkage in Al metallic radius in the alloy by ∼0.17 Å.

KW - distortion

KW - High-entropy alloys

KW - Short-range order

KW - structure-property relationship

KW - X-ray synchrotron radiation

KW - RAY-ABSORPTION SPECTROSCOPY

KW - CU ALLOYS

KW - THERMAL-EXPANSION

KW - SOLID-SOLUTIONS

KW - GRAIN-GROWTH

KW - SITE-OCCUPATION

KW - NI ALLOYS

KW - HIGH ENTROPY ALLOYS

KW - HALL-PETCH

KW - ELECTRONIC-STRUCTURE

UR - http://www.scopus.com/inward/record.url?scp=85085200609&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/48f5011a-2012-39e8-b1fd-656a3ff9bf0c/

U2 - https://doi.org/10.1016/j.actamat.2020.04.034

DO - https://doi.org/10.1016/j.actamat.2020.04.034

M3 - Article

AN - SCOPUS:85085200609

VL - 193

SP - 329

EP - 337

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -