Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Mechanical Engineering | en_US |
| dc.contributor.advisor | Jiao, Zengbao (ME) | en_US |
| dc.creator | Wang, Kai Chen | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/12996 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Microstructure and mechanical properties of nanostructured ultrahigh-strength steels | en_US |
| dcterms.abstract | Ultrahigh-strength steel (UHSS) is a unique kind of steel with a tensile strength exceeding 1200 MPa, as well as excellent ductility, toughness, and fatigue resistance. It is frequently employed in the aerospace, petroleum, and other industries, and is an important support for national defense modernization. The production methods of UHSS include micro-alloying and thermo-mechanical processing, and its high strength and work hardening ability make it the preferred material for high-tech industries. However, UHSS is sensitive to various defects and needs to improve its ductility to enhance its safety and stability, especially when its strength exceeds 2000 MPa. In addition, the high cost of preparation also limits its practical application, becoming a challenge for the development of high-end steel industry. | en_US |
| dcterms.abstract | This dissertation investigated the microstructure and mechanical properties of a cold-rolled austenitic ultrahigh-strength steel with the composition Fe-Ni-Al-C. The deformations by cold rolling in the experiments were 0%, 40%, 60% and 87.5% respectively. According to the results, the yield strength of the steel was about 2.1 GPa, and the total elongation was about 30%. Through mechanical tests and the microstructure characterization using scanning electron microscopy and X-ray diffraction, the plastic deformation mechanism of specimens subjected to various cold-rolled deformations was investigated. Within the cold rolling deformation in this experiment, the Fe-Ni-Al-C austenitic steel exhibited no phase transformation and remained as a single-phase austenite. Moreover, as the deformation increased, steel's yield strength and hardness exhibited a significant upward trend, while the ductility did not show a significant change. Overall, this study provides important reference and guidance for the preparation and performance research of austenitic ultra-high strength steel. | en_US |
| dcterms.extent | ix, 64 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2023 | en_US |
| dcterms.educationalLevel | M.Sc. | en_US |
| dcterms.educationalLevel | All Master | en_US |
| dcterms.LCSH | Steel, High strength | en_US |
| dcterms.LCSH | Nanostructured materials | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | restricted access | en_US |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 7476.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 3.64 MB | Adobe PDF | View/Open |
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