Thesis
MWCNT reinforced metal matrix composites using LENS: Case studies on MWCNT-Bronze and MWCNT-A1-12%Si
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/103711
Abstract
Laser engineered net shaping (LENS) was used to fabricate Carbon nanotube reinforced metal matrix composites using metal powders mechanically alloyed with different contents of multi-walled carbon nanotubes (CNTs) as feedstock. Two different metal matrices, Bronze and Al-Si, were reinforced to fabricate free standing bulk structures and coatings respectively. Microstructural observations of the CNT-Bronze composites showed that CNTs were retained in the composite matrix after laser processing. The addition of CNTs showed an enhancement in yield strength, elastic modulus, hardness and strain hardening rate of the composites. Yield strength was compared with predictions of theoretical models, which indicated the presence of load transfer to reinforcements, thermal mismatch and Orowan looping in the composites. Thermal conductivity increased linearly with increase in CNT volume fraction. The mechanical and thermal properties of these composites can be further improved by optimizing the LENS processing parameters. The composites prepared in this study were not completely dense which affected their properties negatively. The tribological properties of Al-12Si improved with the addition of CNTs in the Al-Si matrix. The friction and wear behaviors of the composite were investigated using a pin-on-disk wear tester under dry condition. The tests were conducted at a sliding speed of 40 mm/s under an applied load of 1 N. The experimental results indicated that the friction coefficient of the composite decreased with the addition of CNTs due to the self-lubrication and unique topological structure of CNTs. The volumetric wear rate showed a drastic reduction with the addition of CNTs. Thermal properties showed a significant improvement with CNT addition. The thermal conductivity of Al-Si coated Al-2024 improved by 31 % after 8 vol% addition of CNTs. Thermal properties are a better indicator of the presence of CNTs in the Al-Si matrix. However, any hard evidence of the presence of CNTs in the Al-Si matrix was not obtained.
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Details
- Title
- MWCNT reinforced metal matrix composites using LENS
- Creators
- Abhimanyu Bhat
- Contributors
- Amit Bandyopadhyay (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525060201842
- Language
- English
- Resource Type
- Thesis