Defect microstructures in polycrystalline pure copper induced by high-current pulsed electron beam——the vacancy defect clusters and surface micropores

In this paper, high-current pulsed electron beam (HCPEB) was used to irradiate the polycrystalline pure copper. The vacancy defect clusters of the irradiated surface layer have been investigated by using transmission electron microscopy. Very dense vacancy defect clusters involving square cells, vacancy dislocation loops and stacking fault tetrahedra were formed after HCPEB irradiation. It suggests that the very high stress and high strain rate induced by rapid heating and cooling due to HCPEB irradiation could cause the shifting of whole atomic planes synchronously, which is the probable mechanism of the formation of the vacancy defect clusters. Additionally, it was established by scanning electron microscopy investigations that dense, fine and dispersed micropores on the irradiated surface of pure copper can be successfully fabricated by using HCPEB irradiation. The dominating formation mechanism of surface micropores should be attributed to the formation of supersaturation vacancies within the near-surface introduced during HCPEB irradiation and vacancy migration along grain boundaries and (or) dislocations towards the irradiated surface. The present results indicate that HCPEB technique may become a new method for rapid synthesis of surface porous materials.