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Compositional design of strong and ductile (tensile) Ti-Zr-Nb-Ta medium entropy alloys (MEAs) using the atomic mismatch approach Nguyen, V, Ma, Q, Shi, Z, Song, T, Huang, L and Zou, J 2019, 'Compositional design of strong and ductile (tensile) Ti-Zr-Nb-Ta medium entropy alloys (MEAs) using the atomic mismatch approach', Materials Science and Engineering A, vol. 742, pp. 762-772. Document type: Journal Article Collection: Journal Articles Title Compositional design of strong and ductile (tensile) Ti-Zr-Nb-Ta medium entropy alloys (MEAs) using the atomic mismatch approach Author(s) Nguyen, V Ma, Q Shi, Z Song, T Huang, L Zou, J Year 2019 Journal name Materials Science and Engineering A Volume number 742 Start page 762 End page 772 Total pages 11 Publisher Elsevier BV Abstract New non-equiatomic Ti(25+x)-Zr25-Nb25-Ta(25-x) (x = 0, 5, 10, 15, 20, in at%) medium entropy alloys (MEAs) have been designed using the atomic mismatch approach and fabricated through a conventional arc-melting process. These novel MEAs were derived from a recently developed equiatomic Ti-Zr-Nb-Ta MEA by gradually replacing its Ta content with Ti. Each non-equiatomic MEA solidified as a single solid-solution phase, which was characterised in detail and compared with Pandat simulation and empirical rules. Systematic tensile mechanical property data revealed the existence of a brittle-to-ductile transition for Ti-Zr-Nb-Ta MEAs, i.e., when 15 at% of Ta in the equiatomic Ti25-Zr25-Nb25-Ta25 MEA was replaced by Ti to become a Ti40-Zr25-Nb25-Ta10 MEA. The transition occurs corresponding to a small reduction in atomic mismatch from 4.72% to 4.65% but a signficant drop in nanoindentation hardness from 4.2 GPa to 3.5 GPa. In particular, both the as-cast Ti40-Zr25-Nb25-Ta10 and Ti45-Zr25-Nb25-Ta5 MEAs exhibited excellent tensile strain to fracture (>18%) and tensile strength (>900 MPa) with much reduced density compared to the brittle Ti25-Zr25-Nb25-Ta25 MEA. They are both among a very small number of strong and ductile (tensile strain >15%) HEAs reported to date. Their tensile mechanical properties can be further tuned by adjusting the atomic mismatch of the resulting single solid-solution phase in conjunction with the improved understanding of the microstructures of these MEAs. Subject Metals and Alloy Materials Keyword(s) High entropy alloys (HEAs) Medium entropy alloys (MEAs) Microstructure Mechanical properties Crystal structure DOI - identifier 10.1016/j.msea.2018.11.054 Copyright notice © 2018 Elsevier B.V. All rights reserved. ISSN 0921-5093 Related Links Link Description https://doi.org/10.1016/j.msea.2018.11.054 Link to Published Version   Versions Version Filter Type Thu, 21 Feb 2019, 13:23:56 EST Tue, 12 Mar 2019, 23:17:11 EST Filtered Full Citation counts:   Cited 6 times in Thomson Reuters Web of Science Article | Citations Cited 0 times in Scopus Article Altmetric details: Access Statistics: 32 Abstract Views  -  Detailed Statistics Created: Thu, 21 Feb 2019, 12:10:00 EST by Catalyst Administrator