Abstract
Friction stir processing (FSP) is modified to produce various grain sizes of aluminum matrix composites (Al-Al2O3, Al-Zn-Al2O3 and Al-Zn) ranging from 300 nm to 3£gm. The microstructures of the composites were characterized using SEM and TEM. Tensile tests were performed to evaluate the mechanical properties of these composites.
In the Al-Al2O3 system, it was found that the nano-scale alumina made it very effective to accumulate dislocations within grains during deformation, and resulted in increasing working hardening rate which is very critical to extend uniform elongation for materials with submicron grain sizes.
In the Al-Zn-Al2O3 system, addition of Zn which dissolved into Al matrix to form solid solution and subsequently uniformly distributed G-P zones can improve strength and uniform ductility to some extent, comparing to those without addition of Zn. In addition, the relaxed and dislocation-free boundaries were observed regardless the existence of Al2O3 particles on boundaries. As a result, ko derived from Hall-Petch equation from various strain region decrease as Zn increases.
In the Al-Zn system, experimental evidence suggests that increasing Zn content from 0 to 15wt% can enhance the total elongation but not uniform elongation as a result of the uniform spreading of the fine slip bands all over the gauge length and the contribution of grain boundary sliding (GBS) at RT. The relaxed and dislocation-free boundaries and GBS are attributed to the combination of high fraction of high-angle GBs and high GB diffusion to help fast dislocations annihilation at boundaries.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0629109-132350 |
| Date | 29 June 2009 |
| Creators | Hu, Che-ming |
| Contributors | Liu-Wen Chang, Wei-Te Wu, Chih-Ching Huang, Shian-Ching Jang, Po-We Kao, New-Jin Ho |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0629109-132350 |
| Rights | not_available, Copyright information available at source archive |
Page generated in 0.0061 seconds