Optimization of Niobium-Based In-Situ Composites for High-Temperature Applications
Final rept. 1 Jan 2000-31 Dec 2002
SOUTHWEST RESEARCH INST SAN ANTONIO TX
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A computational material science approach, involving the application of several material models, was utilized to optimize the oxidation, fracture, and creep resistance of Nb-based in-situ composites. Using this computational approach, several candidate Nb-based, in-situ composites were designed and fabricated. The microstructure, oxidation, and fracture properties of the candidate alloys were characterized and evaluated. Both experimental data and theoretical modeling indicated that the fracture resistance of Nb-based in-situ composites is enhanced by a Ti addition, but is reduced by a high Cr addition, while a high Cr content enhances the oxidation resistance. A high volume fraction of intermetallics in the Nb-based in-situ composites enhances the oxidation resistance but reduces the fracture resistance. The fracture and oxidation resistance of Nb-based in-situ composites could not be optimized simultaneously because of opposite effects of Ti and Cr additions as well as the Nb solid solution and intermetallics Laves and silicides on the fracture and oxidation resistance of the in-situ composites. The theoretical results suggest that a microstructure of fine shearable sub-micron-sized precipitates embedded in a Nb solid solution containing high Ti and Cr contents might be required to improve both the oxidation and fracture resistance of Nb-based in-situ composites.
- Inorganic Chemistry
- Laminates and Composite Materials
- Operations Research