Differences in mechanical properties of nanowires between silver and high entropy alloys and changes in deformation behavior after addition of twin boundaries
| Autor: | Chiu, Yu-Chen, 邱郁宸 |
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| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 Recently, with the development of nano technology, people pay more attention on it because of its high surface area and volume ratio which makes special structure and mechanical properties. While metals with Face-Centered Cubic lattices in nanoscale, there is a structure of five-fold twinned. Because it has five twin boundaries throughout the entire nanowire, its mechanical properties are different from those of single crystal. Besides, we not only simulate the difference of pure element nanowires, but explore the multi-element High entropy alloys nanowires which is difficult to synthesize in experiments. In recent years, it has been found that a multi-element high-entropy alloys nanowires can be grown by thermal evaporation. High entropy alloys breaks the past recognition that materials would become more brittle with more types of alloys. Its superior mechanical properties such as strength, ductility, and low temperature toughness are better than traditional alloys. Our research focuses on comparing materials with outstanding mechanical properties and getting to know more about their unique characteristics. Molecular dynamics (MD) simulation was used to compares the mechanical properties and deformation behavior of single crystal silver nanowires and high-entropy alloys nanowires of the same size by stretching. and changes in deformation behavior after addition of twin boundaries. The simulation results show that the material becomes significantly stronger as well after adding twin boundaries to nanowires. It is mainly because the movement of dislocation is blocked by the twin boundaries. What’s more, we also discovered that twin boundaries restrict the deformation behavior of the nanowires. However, the deformation behavior between adding-twin-boundaries nanowire and original nanowire is extremely different. Finally, by simulating the nanowires at different temperatures and strain rates, we learned the difference of nanowire deformation behavior in different variables. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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