Phase segregation of aged MgCSZ–MgO directionally solidified eutectic composites
The improvement of the thermomechanical properties of Mg-partially stabilized zirconia after appropriate thermal treatments is well known. Most studies in this subject have been conducted in polycrystalline materials produced by solid-state reaction. In this work, we analyze the segregation behavior...
| Autores: | , , , |
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| Tipo de documento: | artigo |
| Estado: | Versão publicada |
| Data de publicação: | 2025 |
| País: | España |
| Recursos: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositório: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/390170 |
| Acesso em linha: | http://hdl.handle.net/10261/390170 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Ageing Mechanical properties Eutectics MgO Mg2Zr5O12 ZrO2 |
| Resumo: | The improvement of the thermomechanical properties of Mg-partially stabilized zirconia after appropriate thermal treatments is well known. Most studies in this subject have been conducted in polycrystalline materials produced by solid-state reaction. In this work, we analyze the segregation behavior and mechanical properties of solidified eutectic composites of the ZrO2–MgO system, where MgO lamellae or fibers are embedded into a cubic Mg-stabilized zirconia (MgCSZ) containing ∼18 mol% MgO. The eutectics have been aged at 1240 or 1225°C for periods varying between 2 and 24 h. This treatment results in the progressive phase separation of the MgCSZ matrix into different mixtures of tetragonal (t), monoclinic (m), δ (Mg2Zr5O12), and MgO phases. Two types of segregation are observed, according to whether the Mg-rich phase is the metastable δ phase (type I) or MgO (type II). Both types may coexist in the same sample but type I predominates at 1240°C and type II at 1225°C. Type I is mainly of the t + δ type, although for long ageing time the t precipitates transform to monoclinic symmetry, resulting in a final m + δ segregation scheme. In type II segregation, the monoclinic phase is the main Mg-poor product. Hardness and toughness have been studied by the Vickers indentation method. The indentation fracture toughness KIC increases progressively with ageing time and for 24 h treatment is more than doubled with respect to the as-processed eutectic, while the hardness decreases slightly. |
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