Short-range chemical order and local lattice distortion in a compositionally complex alloy. (July 2020)

• Record Type: Journal Article
• Authors: Fantin, Andrea; Lepore, Giovanni Orazio; Manzoni, Anna M.; Kasatikov, Sergey; Scherb, Tobias; Huthwelker, Thomas; d'Acapito, Francesco; Schumacher, Gerhard
• Is Part Of: Acta materialia. Volume 193(2020)
• Page Start: 329
• Page End: 337
• Publication Date: 2020-07
• Subjects: High-entropy alloys -- Short-range order -- X-ray synchrotron radiation -- structure-property relationship -- distortion; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2020.04.034
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: This work presents an X-ray absorption spectroscopy study on a single-phase state of the Al8 Cr17 Co17 Cu8 Fe17 Ni33 compositionally complex alloy, focused on the local crystal structure around each alloying element. The comparison of 1 st 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 Al8 Cr17 Co17 Cu8 Fe17 Ni33 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. 1 st 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 Al8 Cr17 Co17 Cu8 Fe17 Ni33, 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. Graphical abstract: Image, graphical abstract