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Dissertation
Spray forming of metal matrix composites: modeling and experimental studies
Doctor of Philosophy (Ph.D.), Drexel University
1994
DOI:
https://doi.org/10.17918/00009565
Abstract
Spray deposition via the OspreyTM process is a potential technology for developing Metal Matrix Composites (MMCs). Advantages of this approach include a near net shape capability, fine scale microstructure devoid of segregation and a uniform distribution of the second phase reinforcement. In this study the fabrication of particulate reinforced MMCs was evaluated by injecting inert or reactive particles into metal spray droplets. A model has been developed to quantify criteria for the penetration of solid particles into the liquid droplets of the spray in the atomizing zone. This is of importance since the scale of the dispersion of reinforcement in the metal matrix is dictated by the extent to which solid particles penetrate the liquid droplets of the spray. The different forces considered in developing this penetration model are the surface tension, hydrostatic, gravitational and the retarding (drag) force. The model identifies particle droplet wettability, particle-droplet relative velocity, particle size and density, as key material/process parameters in determining the degree of penetration. An assessment of the penetration model was made using three different sprays (Cu, Cu-6w/o Ti and Fe-5w/o Ti) and seven species of injected particles (Cu, W, Al2O3, Ni-coated Al2O3, Ta, Fe-2.5w/o C and B4C). Resulting microstructure in the preform and the overspray particles were characterized in terms of the distribution of the reinforcing phase. Injection of cold inert or reactive particles into the liquid droplets alters the thermal condition of the spray. Thus the spray model was modified in order to quantify the effect of the injected particles on spray enthalpy. The modified model predicts the process parameters (melt superheat, gas:metal ratio) required in order to produce preforms with a minimum level of porosity.
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Details
- Title
- Spray forming of metal matrix composites
- Creators
- Shivanand I. Majagi
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xviii, 160 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888985304721