ABSTRACT

TECHNICAL: This program is a renewal of a previously funded program (DMR-0206826). The processing and fabrication of certain alloys and layered composites are inordinately expensive because of the sophisticated methodologies associated with existing processing techniques for these materials. The reactive metals including titanium are a prime example. They are difficult to process in the molten state because they react with crucible linings, as well as with oxygen and nitrogen in air, therefore vacuum systems and water-cooled crucibles must be used to produce titanium and titanium alloy ingots. Other materials that are difficult to process by conventional techniques are the intermetallic compounds. The research from the previous grant has provided vital information for cold roll bonding/reaction annealing as a simplistic processing technique for binary Ti/Al intermetallic sheet materials. Although a simple, less time consuming processing method, for intermetallic sheet materials has been developed, much more work is required to fully understand all of the parameters that affect the process. For example, texture has been known to develop in metals as a function of rolling. However, the previous study did not address the effects of texture on processing. In addition, an in-depth study of the effects of the development of ultra-fine grain structures as a result of severe deformation from multiple cold roll bonding is necessary. Also, preliminary work by the PI has shown that the technique developed in the previous grant for processing binary Ti/Al intermetallic materials has promise for successfully processing ternary intermetallic materials, primarily the Ti-Al-Nb system. The model developed in the previous grant only considered multi-layered bi-metal composites. Specific objectives of this program are: 1. Development and optimization of the cold roll bonding/reaction annealing process for making ternary Ti-Al-Nb sheet materials. 2. Determination of the effects of texture and ultra-fine grain structure on the microstructure and mechanical properties of the processed sheet. 3. Modify the existing model for cold roll bonding to accommodate three different types of elemental sheets. NON-TECHNICAL: As a class of materials, intermetallic compounds and alloys are of high technological interest because they are light in weight (low density) and maintain high strength levels at elevated temperatures (>1100 C). Intermetallics have considerable potential in numerous aerospace, structural, and high temperature applications. However, the lack of breakthroughs in cost-effective processing techniques are partially responsible for the lack of their wide spread use in industry. Research will provide vital information for the further development of cold roll bonding/reaction annealing as a simplistic processing technique for advanced metals and materials. This technique can be scaled-up to create large sheets of Ti/Al/Nb intermetallics, as well as other intermetallics, which can be used to fabricate various items for marine, aerospace, structural and high temperature applications. By developing this simple, less time consuming processing method, production costs for these materials will be decreased significantly. The technique can potentially have a significant impact on alloy systems that are presently too difficult or too expensive to process using existing, or conventional techniques. It could lead to a significant increase in the practical applications and further development of intermetallic compounds in addition to numerous other alloy systems. The modeling component of the research should lead to predictive methods for roll bonging numerous combinations of several different types of thin metallic foils. The program will also lead to the teaching and training of graduate students and undergraduate students.

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