Direct Observation of Oxygen Atoms Taking Tetrahedral Interstitial Sites in Medium‐Entropy Body‐Centered‐Cubic Solutions. Issue 13 (17th February 2023)

• Record Type: Journal Article
• Authors: Liu, Chang; Cui, Jizhe; Cheng, Zhiying; Zhang, Bozhao; Zhang, Siyuan; Ding, Jun; Yu, Rong; Ma, En
• Is Part Of: Advanced materials. Volume 35:Issue 13(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-17
• Subjects: body‐centered‐cubic metals -- electron ptychography -- high‐entropy alloys -- interstitials -- medium‐entropy alloys; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202209941
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Interstitial solutes, such as carbon in steels, are effective solid‐solution hardening agents. These alloying elements are believed to occupy the octahedral interstices in body‐centered‐cubic (bcc) metals. Using deep‐sub‐angstrom‐resolution electron ptychography, here the first experimental evidence to directly observe individual oxygen atoms in a highly concentrated bcc solid solution—the (TiNbZr)86 O12 C1 N1 medium‐entropy alloy (MEA)—is provided, whereby the interstitial sites in which the oxygen atoms are located are discerned. In addition to oxygen interstitials residing in octahedral sites, the first unambiguous evidence of a switch in preference to the unusual tetrahedral sites at high oxygen concentrations is shown. This shift away from octahedral occupancy is explained as resulting from the extra cost of strain energy when the requisite displacement of the host atoms is deterred in the presence of nearby octahedral interstitials. Abstract : Interstitial solutes normally occupy the octahedral interstices in body‐centered‐cubic metals. Using deep‐sub‐angstrom‐resolution electron ptychography, this work provides the first experimental evidence to directly observe individual oxygen atoms, and shows a switch in preference to the unusual tetrahedral sites at high oxygen concentrations in a medium‐entropy alloy.