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The oxidation of six NbTi-i refractory medium- and high-entropy alloys (NbTi + Ta, NbTi + CrTa, NbTi + AlTa, NbTi + AlMo, NbTi + AlMoTa and NbTi + AlCrMo) were investigated at 1000 °C for 20 h. According to our observation, increased Cr content promoted the formation of protective CrNbO4 and Cr2O3 oxides in NbTi + CrTa and NbTi + AlCrMo, enhancing oxidation resistance. The addition of Al resulted in the formation of AlTi-rich oxide in NbTi + AlTa. Ta addition resulted in the formation of complex oxides (MoTiTa8O25 and TiTaO4) and decreased oxidation resistance. Meanwhile, Mo’s low oxygen solubility could be beneficial for oxidation resistance while protective Cr2O3/CrNbO4 layers were formed. In NbTi + Ta, NbTi + AlTa and NbTi + CrTa, a considerable quantity of Ti-rich oxide was observed at the interdendritic region. In NbTi + AlCrMo, the enrichment of Cr and Ti at the interdendritic region could fasten the rate of oxidation. Compared to the recent research, NbTi + AlCrMo alloy is a light-weight oxidation-resistant alloy (weight gain of 1.29 mg/cm2 at 1000 °C for 20 h and low density (7.2 g/cm3)).

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: refractory high-entropy alloys, chemical segregation, oxidation

Date published: 2024-09-18

Publisher: MDPI AG

Journal:

• Materials (ISSN: 19961944) vol. 17 issue. 18 4579

Funding:

• the “High Entropy Materials Center”
• the National Science and Technology Council (NSTC) in Taiwan NSTC 112-2927-I-007-504
• the National Science and Technology Council (NSTC) in Taiwan NSTC 110-2221-E-007-020-MY3
• the National Science and Technology Council (NSTC) in Taiwan NSTC 112-2224-E-007-003

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.3390/ma17184579

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Updated at: 2024-10-08 12:31:19 +0900

Published on MDR: 2024-10-08 12:31:19 +0900