Driven Alloys: A Case of Irradiation-Induced Composition Patterns in Binary Systems
|Event Date:||January 26, 2011|
|Speaker:||Anter A. El-Azab, Ph.D.
Department of Scientific Computing
Faculty Member: Materials Science Program
|Speaker Affiliation:||Adjunct Faculty: Mechanical Engineering Department
Florida State University
Driven alloys are multi-component metals kept far from equilibrium by the action mechanical and thermal loading or by particle irradiation. Under these loads, driven alloys respond by forming high densities of defects whose dynamics lead to composition changes, phase transformation and microstructure evolution. This presentation focuses on irradiation-driven thermodynamic instabilities in alloys, which include phase changes and spinodal-like composition patterning instabilities, with a special emphasis on the latter case. These instabilities are particularly important in investigating the behavior of structural alloys and (alloy) fuels in a nuclear reactor environment and the response of alloy thin films to ion beams. Following a brief review of the related experimental and theoretical works, a detailed model of defect and species dynamics in a binary alloy under irradiation will be presented. This model consists of a set of reaction-diffusion equations governing the dynamics of vacancies, dumbbell-type interstitials and lattice atoms under irradiation; such dynamics includes the stochastic generation of defects by collision cascades as well as the defect and atomic reactions and diffusion. A noticeable feature of this model is that the atomic fluxes are derived based on the transitions of lattice defects, a treatment that is significantly different from the way thermal diffusion is classically handled in alloys. For a binary Cu-Au alloy, a miscible system, the model results clearly demonstrate the formation of compositional patterns under high-temperature particle irradiation, with characteristic wavelengths that depend on the irradiation temperature and the strength of cascades. Ongoing development of a more complete theory of species redistribution and phase instability in irradiated alloys based on the principles of non-equilibrium thermodynamics will be highlighted.
Anter El-Azab is a professor of computational materials science at Florida State University. His research interests are in the field of theoretical and computational modeling of defects in materials and his current research includes microstructure evolution in irradiated alloys and ceramics, morphological instabilities in heterogeneous and nanoscale materials, dislocation dynamics and mesoscale deformation of metals, nanoscale thermal transport, and reduced order models in materials science. He worked for six years as a senior scientist with the computational mechanics, applied mathematics and the interfacial and nanoscience groups at the Pacific Northwest National Laboratory. He joined Florida State University in the fall of 2004 as an associate professor of Mechanical Engineering then transitioned to a joint position with the former School of Computational Science and Mechanical Engineering two years later. Currently, he is a full professor with the Department of Scientific Computing (former School of Computational Science) and is a faculty member of Florida State’s graduate program in Materials Science. Anter obtained his Ph.D. degree in Nuclear Engineering in 1994 at the University of California, Los Angeles and his B.S. and M.S. degrees also in Nuclear Engineering at the University of Alexandria.
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2011-01-26 15:30:00 2011-01-26 16:30:00 America/Indiana/Indianapolis Driven Alloys: A Case of Irradiation-Induced Composition Patterns in Binary Systems EE 170