Atomistic simulations of irradiation-induced dislocation loops in zirconium alloys
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Irradiation-induced dislocation loops are important defects that affect zirconium alloys used in the manufacture of major structural components of nuclear reactors. In this thesis atomistic simulations and theoretical modellings are performed to analyze and explain experimental observations made by other authors. The formation and growth of different types of dislocation loops are believed to be responsible for different stages of irradiation damage, and it is necessary to understand their formation and development. However, the fundamental mechanisms behind them are still not fully elucidated. Therefore, the aim of this thesis is to investigate formation and growth mechanisms of different types of dislocation loops under various complex irradiation environments. The background and importance of dislocation loops are introduced in Chapter 1, and a literature review is given in Chapter 2. In Chapter 3, we use both a model of dislocation energy and MD simulations to explore the habit planes of 𝑎-type dislocation loops, while cascade simulations are produced to investigate the effect of irradiation on those loops. In Chapter 4, cascade simulations with different PKA energies were performed to interact with pre-existing 𝑎-type loops; 𝑐-component interstitial loops were only observed under the condition of high-energy PKAs. The role of Ni segregation on the stability of dislocation loops in the Zr-Ni binary system is elucidated by employing molecular dynamics/Monte Carlo simulations in Chapter 5. In Chapter 6, the formation mechanisms of 𝑎-type and 𝑐-component dislocation loops in α-Zr were investigated by a combination of a fully constrained analytical model and molecular dynamics simulations. In Chapter 7, the effect of existing microstructural elements on primary damage production in α-Zr —and vice-versa—is assessed by molecular dynamics simulations. For better replicating in-reactor alloys, the influence of iron segregation to the dislocation loops is assessed. The main conclusions of this thesis are described in Chapter 8, and some interesting future work is also discussed.
URI for this recordhttp://hdl.handle.net/1974/24858
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