Study Of Irradiation Damage Induced By He2+ion Irradiation In Bulk Cu-, Zr-and Co-based Metallic Glasses

Metallic glasses have high strength, excellent resistances to etching and irradiation due to the metastable structure features of long-range disorder and short-range order, which can be used as a highly feasible material of the first wall of fusion reactor. This paper used the He2+ion with an energy of500keV for irradiating different series of metallic glasses ((Cu47Zr4sAl8)98.5Y1.5, Zr64Cu17.8Ni10.7Al7.5, Co61.2B26.2Si7.8Ta4.8) and metallic W for comparison, the most promising candidate plasma facing material in the reactor, at the irradiation fluences of2×1017,1×1018and2×1018ions/cm2. Therefore, it is of great significance to look for series of metallic glass with good irradiation resistance.With the computer code SRIM, the ion range from the surface of Cu-, Zr-, Co-based metallic glasses respectively are1.19μm,1.20μm,1.12μm, while that of the tungsten is0.76μm. The DPA (displacement per atom) of Cu-, Zr-, Co-based metallic glasses and metallic W irradiated with He2+at the fluence of2×1018ions/cm2are62.9,56.9,45.3,20.8, respectively. The phonon energy loss distribution and vacancies distribution are also simulated by SRIM. In this paper, the X-ray diffractometer, the scanning electron microscope, transmission-type electron microscope and the atomic force microscope were used to analyze the surface phase structure and microstructure of He2+irradiated metallic glassesThe main analysis results are following:The three kinds of metallic glasses maintain amorphous state under different irradiation fluences. When the irradiation fluence is2×1018ions/cm2, there’s no obvious radiation damage on the surface of Cu-and Zr-based metallic glass. While there was an apparent damage layer1.35μm away from the surface of the Cu-based metallic glass, and in the metallic glass Zr-based metallic glass, there’s a channel-like damage traces extending1.25μm away from the surface. The result of TEM showed that a large number of helium bubbles stay and accumulate at the end of the ion range. The process of helium bubble coalescence had been observed in HRTEM image of the Zr-based metallic glass. However, roughening occurred on the surface of Co-metallic glass, and the apparent delamination phenomenon appeared in metallic glass Co-based metallic glass. The thickness of damage layer of these three kinds of metallic glasses was approximately the range of helium ions in them. When the irradiation fluence was only1×1018ions/cm2, irradiation damage appeared on the surface of metallic W such as roughening, peeling, flaking, etc. When the irradiation fluence reached2×1018ions/cm2, the surface peeling and flaking of the metallic W became more serious, and even multi-layer peeling appeared.The surface evolution of bulk amorphous alloys under He2+irradiation will be an outcome of a competition between ion bombardment induced surface roughening process and the material transport induced smoothening process. The ρrms of surface of Cu-and Zr-based metallic glass first increased and then decreased with the increase of fluence. While the ρrms of Co-based metallic glass increased with the increase of fluence. After the irradiation of low-fluence (2×1017ions/cm2,1×1018ions/cm2) He2+ion, Cu-and Co-based metallic glass maintained a high reflectivity.The three kinds of metallic glasses used for the experiment had better resistance to He2+irradiation than the metallic W below its glass transition temperature, and Cu-and Zr-based metallic glass had better resistance to He2+irradiation than metallic glass Co-based.