Diffusion Concept in Phase Stability of High Temperature Composites
Abstract
A high-efficiency "diffusion multiple" approach was employed to determine the phase diagrams of nine ternary systems Nb-Ti-Si, Nb-Cr- Si, Nb-Cr-Ti, Ti-Cr-Si, Nb-Si-Al, Nb-Cr-Al, Nb-Ti-Al, Ti-Si-Al, and Ti-Cr-Al. These phase diagrams are very important for the design of Nb silicide based composites and their coatings for advanced military aircraft engines. Most of these ternary systems are very complex-some contain up to 14 phases, thus they also serve as excellent examples to test the applicability of the diffusion multiple approach to such complex systems. A total of seven different diffusion multiples were made to map the phase diagrams of these nine ternary systems. It would take more than a thousand individual alloys to accomplish the same amount of phase diagram mapping. All the equilibrium phases reported in these systems were observed in the diffusion multiples and an extremely large amount of phase equilibrium information was obtained to construct isothermal section phase diagrams. The results clearly demonstrate the applicability of this novel approach to very complex phase diagrams. We have gained extensive experience on how to make diffusion multiples and how to most efficiently analyze such complex systems. The experimental data were used to model thermodynamic parameters for extrapolating the ternary data into multicomponent alloys to provide critical data for computational design of alloys. Our results provide a much clearer picture of the phase equilibria in the Nb-Si-Ti-Cr-Hf-Al composites.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2003
- Accession Number
- ADA414912
Entities
People
- Ji-cheng Zhao
- Melvin R. Jackson
Organizations
- General Electric