Analysis and Modeling of Phase Stability and Multiphase Designs in High Temperature Refractory Metal-Silicon-Boron Alloys

摘要

For high temperature application beyond the range of Ni-base superalloys, Mo-Si-B alloys with the ternary intermetallic, Mo5SiB2, T2, phase as a key microstructure constituent, offer an attractive property balance of high melting temperature, oxidation resistance and useful high temperature mechanical properties. The fundamental basis of the alloying behavior in T2 including the mutual solid solution with transition metals has been established in terms of the governing geometric and electronic factors. For non- stoichiometric compositions, constitutional defects such as vacancies for Mo- rich compositions control the homogeneity range and play a key role in the development of dislocation and precipitation reactions that directly impact high temperature structural performance. The sluggish diffusion rates within the T2 phase have also been quantified and applied to materials processing strategies. The materials design based on the phase stability, diffusion and defect structure analysis in the Mo-Si-B system can also be applied to the design of new multiphase high-temperature alloys with balanced environmental and mechanical properties.