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Title:Novel precipitate structures in alloys under irradiation
Author(s):Shu, Shipeng
Director of Research:Bellon, Pascal
Doctoral Committee Chair(s):Bellon, Pascal
Doctoral Committee Member(s):Averback, Robert S; Trinkle, Dallas R; Zhang, Yang
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):self-organization
irradiation
Abstract:We investigate the fundamentals of precipitate stability under energetic particle irradiation, towards the goal of better controlling the microstructures of driven alloys. First we focus on an irradiation-induced precipitatewithin- precipitate structure, which is referred to as “cherry-pit” structure. We show by computer simulation and analytical modeling that the formation of cherry-pit structure is a special instance of compositional patterning, and that the conditions for compositional patterning and the formation of cherry-pit structures are related, but different from each other. Then we develop a new kinetic Monte Carlo model, which includes the generation, recombination, and sink elimination of irradiation-induced point defects, as well as ballistic mixing. With this tool we explore the possibility of using point-defect sinks to alter the temperature range where compositional patterns are stable. This novel approach for optimizing radiation-resistant materials is then tested experimentally using a Cu-Ag-W model alloy. Lastly we show that the addition of a high density of W nanoparticles dramatically alters the coarsening behavior of precipitate-hardened Cu-Ag alloys. First, the nanoparticles suppress precipitate growth, but far more surprisingly they induce non-equilibrium Ag wetting layers on grain boundaries. This observation is explained using kinetic Monte Carlo simulations, which show that caging of Ag precipitates by the W nanoparticles suppresses their growth and drives the formation of the wetting layers.
Issue Date:2015-08-27
Type:Thesis
URI:http://hdl.handle.net/2142/88942
Rights Information:Copyright 2015 Shipeng Shu
Date Available in IDEALS:2016-03-02
Date Deposited:2015-12


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