The mechanical properties and behaviors of lightweight metallic alloys are largely dictated by their microstructures at various length scales, ranging from nanoscale precipitate morphologies to microscale grain structures. Therefore, fundamental understanding of the thermodynamic and kinetic mechanisms leading to different types of phase/grain microstructures is an essential step toward identifying processing conditions for producing desired alloys with improved strength and ductility. Proposed work for the Microstructure Modeling node focuses on applying the phase-field method, which has emerged as one of the most powerful computational methods for modeling microstructure evolution because of its simplicity and flexibility in describing the complicated configuration of microstructures. The phase-field technique within the Microstructure Modeling node can predict and understand phase microstructures (e.g., precipitate morphology and distribution) under various thermo-chemical-mechanical conditions and their relation to mechanical properties and provide simulated digital microstructures to other modeling frameworks for mechanical property prediction (e.g., input microstructures for the crystal plasticity modeling).
Because this technique is based on the continuum and diffuse-interface description of microstructures, mesoscale materials phenomena can be simulated without describing detailed atomistic scale mechanisms. For quantitative modeling, materials parameters and thermodynamic energetics (elastic modulus, lattice parameter, interfacial energy, free energy, etc.) either from atomistic/thermodynamic calculations or experiments are always required.
The phase microstructure evolution of lightweight alloys usually involves phase transformations in the presence of structural and/or elastic inhomogeneities, as well as anisotropies (e.g., precipitation in polycrystalline alloys). Recent advances with the phase-field method to elastically inhomogeneous and anisotropic polycrystals [1-3] enable modeling of kinetic materials processes, such as solute diffusion and crystallographic structural change in polycrystalline alloys, which is more realistic in actual engineering applications.
Although commercial or open-source phase-field codes for generic materials processes are available, there is no specific phase-field code directly available to the LightMat Consortium. Because the necessary phase-field models [1-4] for modeling microstructures of lightweight alloys are in place, they can be easily integrated and adapted to simulate microstructure evolution and materials processes for specific alloys of interest.
Name: Tae Wook Heo
- T.W. Heo, S. Bhattacharyya, and L.-Q. Chen, “A phase field study of strain energy effects on solute-grain boundary interactions”, Acta Materialia, 59, 7800 (2011)
- T.W. Heo, S. Bhattacharyya, and L.-Q. Chen, “A phase-field model for elastically anisotropic polycrystalline binary solid solutions”, Philosophical Magazine, 93, 1468 (2013)
- T.W. Heo and L.-Q. Chen, “Phase-field modeling of displacive phase transformations in elastically anisotropic and inhomogeneous polycrystals”, Acta Materialia, 76, 68 (2014)
- Y.Z. Ji, A. Issa, T.W. Heo, J.E. Saal, C. Wolverton, and L.-Q. Chen, “Predicting β′ precipitate morphology and evolution in Mg-RE alloys using a combination of first-principles calculations and phase-field modeling”, Acta Materialia, 76, 259 (2014)