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| Autori principali: | , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2023
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| Soggetti: | |
| Accesso online: | https://arxiv.org/abs/2310.20441 |
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| _version_ | 1866909138799296512 |
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| author | Pshyk, O. V. Vasylenko, A. Kuttel, P. Wicher, B. Schweizer, P. Michler, J. Edwards, T. E. J. |
| author_facet | Pshyk, O. V. Vasylenko, A. Kuttel, P. Wicher, B. Schweizer, P. Michler, J. Edwards, T. E. J. |
| contents | Traditionally, increasing compositional complexity and chemical diversity of high entropy alloy ceramics whilst maintaining a stable single-phase solid solution has been a primary design strategy for the development of new ceramics. However, only a handful have shown properties that justify the increased alloying content. Here, we unveil a groundbreaking strategy based on deviation from conventional equimolar composition towards non-equimolar composition space, enabling tuning the metastability level of the supersaturated single-phase solid solution. By employing high-temperature micromechanical testing of refractory metal-based high entropy nitrides, we found that the activation of an additional strengthening mechanism upon metastable phase decomposition propels the yield strength of a non-equimolar nitride at 1000 C to a staggering 6.9 GPa, that is 40 % higher than the most robust equimolar nitride. We show that the inherent instability triggers the decomposition of the solid solution with non-equimolar composition at high temperatures, inducing strengthening due to the coherency stress of a spinodally modulated structure, combined with the lattice resistance of the product solid solution phase. In stark contrast, the strength of equimolar systems, boasting diverse chemical compositions, declines as a function of temperature due to the weakening of the lattice resistance and the absence of other strengthening mechanisms. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2310_20441 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Unlocking ultrastrong high-temperature ceramics: Beyond Equimolar Compositions in High Entropy Nitrides Pshyk, O. V. Vasylenko, A. Kuttel, P. Wicher, B. Schweizer, P. Michler, J. Edwards, T. E. J. Materials Science Traditionally, increasing compositional complexity and chemical diversity of high entropy alloy ceramics whilst maintaining a stable single-phase solid solution has been a primary design strategy for the development of new ceramics. However, only a handful have shown properties that justify the increased alloying content. Here, we unveil a groundbreaking strategy based on deviation from conventional equimolar composition towards non-equimolar composition space, enabling tuning the metastability level of the supersaturated single-phase solid solution. By employing high-temperature micromechanical testing of refractory metal-based high entropy nitrides, we found that the activation of an additional strengthening mechanism upon metastable phase decomposition propels the yield strength of a non-equimolar nitride at 1000 C to a staggering 6.9 GPa, that is 40 % higher than the most robust equimolar nitride. We show that the inherent instability triggers the decomposition of the solid solution with non-equimolar composition at high temperatures, inducing strengthening due to the coherency stress of a spinodally modulated structure, combined with the lattice resistance of the product solid solution phase. In stark contrast, the strength of equimolar systems, boasting diverse chemical compositions, declines as a function of temperature due to the weakening of the lattice resistance and the absence of other strengthening mechanisms. |
| title | Unlocking ultrastrong high-temperature ceramics: Beyond Equimolar Compositions in High Entropy Nitrides |
| topic | Materials Science |
| url | https://arxiv.org/abs/2310.20441 |