Interfacial reactions during the liquid infiltration of titanium matrix composites. Ph.D. Thesis
A rapid infrared forming process has been developed for the fabrication of ceramic fiber reinforced titanium alloy matrix composites. Using this technique, composites can be fabricated at a low cost into complicated shapes. Compared to the titanium matrix composites fabricated by solid state processes, composites fabricated by this technique exhibit smaller as-fabricated reaction zones and comparable mechanical properties. In order to develop a fundamental understanding of reactions during liquid state processing of titanium matrix composites as well as for determining the potential for commercialization of the rapid infrared forming process, interfacial reactions during processing were thoroughly examined. During the fabrication of carbon fiber reinforced titanium alloy matrix composites, it was observed that the fibers react with the alloy and form a protective TiC layer which prevents the fibers from coming in direct contact with the molten alloy. Further degradation of the fibers was found to be controlled by the diffusion of carbon across the reaction product. A cylindrical model has been proposed to predict the extent of reaction in these composites. In uncoated SiC fiber (SCS-0) reinforced composites, a continuous layer of reaction product did not form at the fiber surface and large areas of the fibers were dissolved by the molten alloy. Examinations revealed that the interface consists of radially propagating scalloped dissolution fronts. A self sustaining exothermic dissolution model has been proposed to explain the observed interface. In SCS-6 fiber reinforced composites, it was found that although a continuous layer of the reaction product does not form, self sustaining exothermic dissolution does not occur. A physical model has been proposed to explain the dissolution of the carbon rich coating in these composites.
- Research Organization:
- Cincinnati Univ., OH (United States)
- OSTI ID:
- 121803
- Resource Relation:
- Other Information: TH: Ph.D. Thesis; PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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