Vacancy Clusters Defects Of Aluminum Induced By High-energy Beam Radiation

When the energetic beam irradiates crystal materials, the so-called irradiation damage effects are normally produced. The energy of energetic beam transfers to the crystal lattice, particle beam can cause strong response and produce interstitial atoms and vacancies (Frenkel defects) in the crystal lattice by atom collisions or rapidly heating and cooling. If previously formed interstitial atoms and vacancy defects can not mutually compound and annihilate in the location which form or other lattice location, but gather into more crystal defects according to some way, at this point certain physical or mechanical performance of the materials will be damaged. In strong nuclear beam irradiation and cosmic ray irradiation environment, the failure process and service life of materials caused by irradiation is a dominate topic which decide the nuclear energy security and astronavigation safe. The research for irradiation damage through microstructure changes of irradiated materials is widely acknowledged to be one of the most effective research techniques. Based on the observation of microscopic structure, it can reveal the characteristics and evolution of crystal defects, therefore a more well understanding of the material characteristics of irradiation damage.Significant changes of materials properties by energetic beam are universally concerned by the fields of the space technology and nuclear technology. Vacancy cluster defect by irradiation is the most common structural defect in metal. Under normal circumstances vacancy clusters lead to macro expansion of materials, which seriously reduces the mechanical properties and the physical properties, therefore, the formation and evolution of vacancy cluster defects, and the relationship between that and other defects is the key factor for research material properties and servant life, which has become an important study of energetic beam irradiation research . In this paper, we studied the micro - structure of the EUV absorption filter film of very ultraviolet (EUV) solar telescopes by irradiated. Filter is the key component of space solar telescope, and its performance can affect the image quality of space solar telescope. Filter is almost completely exposed to the outer space environment, in LEO conditions filter directly irradiate by proton beam. Many optical system flights in space for some time, image quality will be lowered, one of the most important reasons is performance degradation of filters by energetic beam irradiation. As the thin film filter of space solar telescope is more expensive and easily damaged, hence in this paper, we choose high-purity aluminum film as experimental samples, which are irradiated by proton beam produced by a space environment simulation device. We observe and analyze the crystal defects, especially vacancy clusters which are formed in materials induced by proton beam, discuss the deformation and evolution behave of the structural defects and its relationship between that and material deformation behavior. Vacancy dislocation loops can be induced by Proton irradiation in Al films.Within the scope of the experiment, the number density of dislocation loop increases with the radiation dose increases. Vacancies tend to form the larger vacancy defect clusters. The dislocation density increases with the radiation dose increases. The cellular structure appears at higher dose of irradiation. There is a small orientation difference between the cell walls, the relation between the cellular structure and degradation of mechanical properties of materials is close.The pure aluminum with various pre-deformation extents was irradiated with 4J/cm2 energy density by using a high-current pulsed electron beam (HCPEB) source. The effect of the structure defects on the crater formation was investigated using optical microscopy and scanning electron microscopy (SEM). The crater distribution density along with the grain boundary and slipping band of dislocation were determined. The experimental results suggest that the crater distribution density increases with increasing the pre-deformation extents of the aluminum sample, and the crater prefers to form at the structure defects such as grain boundary and slipping band of dislocation. As a result of these experiments, the most probable mechanisms of crater formation on the surface of pure aluminum were established. HCPEB bombardment may not induce plastic deformation twins in the melting pure aluminum surface, induced stress is over 1GPa, and impact stress is the underlying cause which causes changes of deep properties and organization of materials.