Validated phase diagrams are the bedrock of alloy design and optimization. Determination of equilibrium and non-equilibrium phase transformations will include four major steps: (1) first-principles calculation to determine ground-state energies of compounds; (2) experimental determination of solid-solid and solid-liquid transformation temperatures, solubility limits, heat capacity, absolute entropy at 298K, enthalpy of mixing for liquid, enthalpy of formation for compounds, and chemical potentials; (3) assemble CALPHAD database of desired systems; (4) utilize phase diagrams and non-equilibrium chemical partitioning calculations to determine phase transformation under varying degrees of chemical potentials or cooling rate.
For systems of interest, see Table below, databases to compute phase diagrams to guide new processing routes of critical materials will be developed while concurrent high-throughput experiments to test its predictive capabilities are undertaken. Increasing complexity can be readily added to existing databases, i.e., ternary systems developed from 3 binaries, etc. Validated phase diagrams and associated process models will provide industrial partners new tools to develop new materials and processing streams as well as tailor existing technologies.
Mentor: Shihuai Zhou, Assistant Scientist III, Ames Laboratory