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 Title: Multi-scale investigation of vacancy-mediated diffusion of Si in Ni near an edge dislocation Author(s): Li, Zebo Director of Research: Trinkle, Dallas R Doctoral Committee Chair(s): Trinkle, Dallas R Doctoral Committee Member(s): Pascal, Bellon; Averback, Robert S; Zhang, Yang; Heuser, Brent J Department / Program: Nuclear, Plasma, & Rad Engr Discipline: Nuclear, Plasma, Radiolgc Engr Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Dislocation, climb, diffusion, point defect, solute segregation Abstract: During the last decade, studies have focused the development of creep-resistant alloys that can tolerate the high temperatures and high irradiation doses within nuclear reactors. One important mechanism of irradiation creep is the migration of dislocations, which arises as a direct consequence of point-defect diffusion near dislocations and is also affected by the presence of solutes. In this work, we develop a multi-scale model which is able to simulate the diffusion of point-defects and solute atoms in the dislocation strain field. We first use kinetic Monte Carlo simulations to investigate the strain effects on the transport coefficients for vacancies and Si in FCC Ni. We then use a mesoscale model, which takes the strain-dependent transport coefficient computed by self-consistent mean field calculations, to model the irradiation induced solute segregation around an $\frac{a}{2}[1\bar{1}0](111)$ edge dislocation in FCC Ni-Si alloy. At last, we extend the mesoscale model into an multi-scale approach by coupling it to a discrete model which captures the thermally activated atomic transitions and reactions in the dislocation core. We use the multi-scale approach to investigate the climb motion of an $\frac{a}{2}[1\bar{1}0](111)$ edge dislocation in FCC Ni-Si alloy, induced by irradiation and by an externally applied stress. We also quantify the effect of solute on the climb velocity. Issue Date: 2017-09-06 Type: Thesis URI: http://hdl.handle.net/2142/99175 Rights Information: Copyright 2017 Zebo Li Date Available in IDEALS: 2018-03-13 Date Deposited: 2017-12
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