Molecular Dynamics Simulation Of Irradiation Damage In Cu

One of the key factor in nuclear safety is the irradiation damage of materials un-der extreme irradiation does. Irradiation produces point defects (vacancy and intersti-tial), which migrate, aggregate, and eventually cause degradation of materials integrity and performance. Understanding irradiation damage process and mechanical property change after irradiation is prerequisite for designing irradiation-tolerant materials. With molecular dynamics simulations, the primary irradiation damage and mechanical re-sponse of irradiated Cu under static and dynamic loading are investigated.Due to short interatomic distance in displacement cascades, EAM potential is smoothly splined to ZBL potential when interatomic distance is smaller than 0.5 A. The response of elastic prestrained single-crystal Cu to irradiation is investigated. Under uniaxial tension, irradiation induces such defects as frenkel pairs, dislocations, stacking faults, twins and voids. Twins form through overlapping of different stacking faults. And voids nucleate via liquid cavitation. At a given prestrain, there exists a critical energy of primary knock-on atom (PKA) for dislocation activation.The interaction between displacement cascades and a set of Σ3(110) tilt grain boundaries (GB) has been studied. GBs exhibit pronounced preferential absorption of interstitials, which depends on initial PKA distance from GB plane and inclination angle, and leaving excess concentration of vacancies in grain interior. GB migration occurs when displacement cascades overlap with a GB plane, ad induced by recrystal-lization of thermal spike, and concurrent asymmetric grain growth.After irradiation, yield stress and yield strain of perfect single-crystal Cu decrease. Interstitials dominate the decrease of yield stress and yield strain, because of more dis-tortion and higher stress concentration around them. Young’s modulus of irradiated Cu decrease linearly with the increment of frenkel pair concentration. Dependence of yield stress (yield strain) on frenkel pair concentration has the same tendency, while the relation is not linear.In this thesis, the influence of He bubble on materials shock response has also been explored. Under shock loading, the internal He pressure of interior bubble im-pedes bubble collapse, while near-surface He bubble may burst and form high velocity ejecta. When internal He pressure is enough large, near-surface He bubbles may also burst without shock loading, leaving cavities on the surface. Under shock loading, these cavities may induce jetting. Microstructures of cavities, e.g. geometry and crystal struc-ture, have pronounced effects on such parameters as velocity and shape of jet.These conclusions of this thesis can be used to explain irradiation induced void nucleation and grain boundary migration reported in recent experiments, and provide basic data and theory for future development of nuclear materials.