He2+ irradiation induced microstructure evolution in sub-surface layer of the coarse-grained tungsten accessed by synchrotron GIXRD and GISAXS

Abstract

In this study the microstructure evolution in sub-surface layer of the coarse-grained W after irradiation of 400 keV He2+ at different fluences and temperatures was assessed by synchrotron grazing incident X-ray diffraction (GIXRD) and grazing-incidence small-angle X-ray scattering (GISAXS). The splitting of GIXRD peaks obtained at different incident angles indicates that the un-irradiated coarse-grained W exhibits a compression strain state in the near surface and the He ions irradiation results in a lattice swelling which is more severe at higher irradiation temperature and fluence. The GISAXS results combined with the TEM analysis indicate that after irradiation at room temperature, uniformly distributed high density dislocation loops with an average radius of about 3.7 nm were formed due to the extrusion of He-V clusters. After irradiation at 400 °C, high density He bubbles with radii between 1 and 3 nm were formed in the sample interior, while large blisters appeared near the surface. This work provides a reference for the study of irradiation damage in the sub-surface layer of W alloys via synchrotron GIXRD and GISAXS.