Stability of Uranium Silicides During High Energy Ion Irradiation

Abstract

ABSTRACTChanges induced by 1.5 MeV Kr ion irradiation of both U3Si and U3Si2 have been followed by in situ transmission electron microcopy. When irradiated at sufficiently low temperatures, both alloys transform from the crystalline to the amorphous state. When irradiated at temperatures above the temperature limit for ion-beam amorphization, both compounds disorder, with the Martensite twin structure in U3Si disappearing from view in TEM. Prolonged irradiation of the disordered crystalline phases results in nucleation of small crystallites within the initially large crystal grains. The new crystallites increase in number during continued irradiation until a fine grain structure is formed. Electron diffraction yields a powder-like diffraction pattern that indicates a random alignment of the small crystallites. During a second irradiation at lower temperatures, the small crystallizes retard amorphization. After 2 dpa at high temperatures, the amorphization dose is increased by over twenty times compared to that of initially unirradiated material.