| Significant cost savings can be realized in alloy design and processing by using computer modeling, reducing the amount of experimental effort necessary. Dr. Wang's research projects focus on the development of computational models and simulation techniques, validated by experimentation, for fundamental understanding of the mechanisms underlying microstructural evolution and for practical applications to microstructural engineering of advanced materials. Supported by the National Science Foundation (NSF), the Air Force Office of Scientific Research (AFOSR), the Air Force Research laboratory (AFRL), the National Institute of Standards and Technology (NIST), the NSF San Diego Supercomputing Center and the Ohio Supercomputing Center, his current research projects include (a) microstructure development during structural phase transformations and microstructure - dislocation interactions during exposure to temperature and stress in high-temperature Ni-based superalloys and Ti alloys, (b) microstructure development in advanced multi-domain magnetic materials under applied fields, (c) interdiffusion microstructure and diffusion path in multi-component and multiphase coatings and multi-layers and (d) grain growth in anisotropic media and migration of interfaces and dislocations with segregating defects. Dr. Wang's work ties closely to the University's newly established research and education thrust on computational materials science and engineering. Courses Taught
Publications
Presentations Links to Research Websites Materials for Future Magnetic Recording Application Research Project Highlights Pattern Formation During Structural Transformations
Numerical experiments have allowed the development of a fundamental understanding of mechanisms involved in microstructural development during various structural transformations. The micrograph on the left shows the formation of herring-bone structure during martensitic transformation through an autocatalytic mechanism (the micrograph shows nine consecutive 2-D cross sections of a 3-D cube). The micrograph on the right shows the complex domain structure formed during a coherent hexagonal to orthorhombic transformation. The interaction among the strain fields generated by different orientation domains produces very interesting self-accommodating star patterns which are in striking agreement with the experimental observations. An example is given in the small inset (courtesy of S. Amelinckx).  |  | Oxide-Based Electroceramics
In collaboration with the NSF Center for Industrial Sensors and Measurements (CISM) at OSU, continued effort is being made in integrating modeling of microstructural evolution, surface reaction, and electrical conduction processes in solid state gas sensors. Shown on the left is an example where the electrical resistivity of a porous granular material is calculated simultaneously as the microstructure evolves during sintering. The modeling work has facilitated sensor optimization by predicting the behavior of gas sensors as a function of microstructure, temperature, and addition of dopants. a)  | b)  |
| Simulated microstructural evolution during sintering of electroceramics (a) and the corresponding relative resistivity change (b). | | Grain Growth in Anisotropic Media
The dynamics and morphology of grain growth with anisotropic energy and mobility of grain boundaries have been investigated using a generalized phase field model in which both inclination and misorientation of the boundaries are considered. We found that energy anisotropy has a much stronger effect than mobility anisotropy. In the case with mobility anisotropy the average grain area grows linearly with time, as in an isotropic system, but grains grow in a non-self-similar manner leading to grain shape anisotropy. In the case with energy anisotropy grain growth is not linear anymore and much stronger shape anisotropy develops. Ni-Based Superalloys and gamma-TiAl Intermetallic Alloys
Software programs have been developed for simulating the complex microstructural development in high-temperature Ni-based superalloys and gamma-TiAl intermetallic alloys. The micrograph below on the left shows a comparison between the experimentally observed (A, courtesy of M. Fahrmann) and simulated (inset, B) microstructure of gamma' precipitates developed during isothermal aging. In collaboration with the Air Force Research Laboratory at Wright-Patterson AFB, the models are currently being extended to simulate the overall transformation kinetics under varying processing conditions such as continuous cooling. The micrograph on the right shows an example of the lamellar structure developed in gamma-TiAl, where different colors represent the six orientation variants of the gamma phase.  |  | | 