The Phase Field Method: Towards a Tool for Materials Design
Abstract
Central to designing new materials is the ability to link the processing of a material to its structure in alloys of commercial importance that typically that contain many elements and phases. The processing sets the composition of the phases, their spatial distribution, and their morphology which, in turn, affect the properties and performance of an alloy. For example, the morphology of ?’ particles and the channel width between ?’ particles play critical roles in the high temperature creep properties of Ni-base superalloys. Ti alloys display an array of second phase morphologies from basket weave laths to Widmanstaten plates. Nearly every structural material is polycrystalline. The average size of the grains clearly affects the strength of the alloy, yet predicting the grain size distribution and morphology during isothermal grain growth, much less as a function of thermal processing, remains a challenge. Many materials are used in their cast form, e.g. Ni-base superalloys for turbine blades, and materials printed by Additive Manufacturing (AM). Thus, the compositional inhomogeneities that result from the solidification process cannot be removed or, as in the AM case, require a costly long-term heat treatment. Understanding the chemical segregation patterns resulting from solidification in multicomponent alloys is thus of great importance. Phase field methods provide a flexible framework that can potentially address all of these critical issues. The method allows for the complicated morphologies that result from phase transformations and grain evolution to be computed. Moreover, new physics, e.g. stress and electric fields, can easily be added, and topological transformations, such as precipitate merging and splitting, occur naturally. However, challenges remain that will prevent phase field methods to be used routinely in a materials design effort. We propose to develop a computationally efficient phase field method for multicomponent alloys that can be used to follow morphological evolution during both solidification and ?-phase precipitation in the Ti alloys of interest to the Navy. We shall develop a model for grain growth that incorporates all five degrees of freedom of the grain boundary energy. The method will also be able to use the reduced order descriptions of the five degrees of freedom dependence of grain boundary energy to yield a computationally efficient model. Given the flexibility of the phase field models, it will also be possible to address problems suggested by researchers at the Naval Research Laboratory and NSWC-Carderock. In order to foster close interactions, the postdoc supported by the program will spend 3 months per year at either location, and 9 months at Northwestern.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 19, 2018
- Source ID
- N000141812787
Entities
People
- Peter Voorhees
Organizations
- Northwestern University
- Office of Naval Research
- United States Navy