Study of Irradiation Damage Induced by Helium Ion in Fe-based Metallic Glass

The changes in structure and surface morphology of metallic glasses Fe$_{\mathrm{80}}$Si$_{\mathrm{7.43}}$B$_{\mathrm{12.57}}$ and Fe$_{\mathrm{68}}$Zr$_{\mathrm{7}}$B$_{\mathrm{25}}$ before and after the irradiation of He ions with the energy of 300keV were investigated, and were compared with that of the tungsten. In metallic glass Fe$_{\mathrm{80}}$Si$_{\mathrm{7.43}}$B$_{\mathrm{12.57}}$, when the fluence of He ions was up to 4×10$^{\mathrm{17}}$ions/cm$^{\mathrm{2\thinspace }}$(19dpa), crystallization occurred, and a small amount of metastable $\beta $-Mn type phase nanocrystals formed. When the fluence increased to 1×10$^{\mathrm{18}}$ions/cm$^{\mathrm{2\thinspace }}$(47dpa), the quantity of nanocrystals increased and metastable $\beta $-Mn type phase transformed into $\alpha $-Fe phase and tetragonal Fe$_{\mathrm{2}}$B phase. Then orthogonal Fe$_{\mathrm{3}}$B phase and $\beta $-Mn type phase formed and were added to the nanocrystals as the fluence increased to 1.6×10$^{\mathrm{18}}$ions/cm$^{\mathrm{2}}$(69dpa), while metallic glass Fe$_{\mathrm{68}}$Zr$_{\mathrm{7}}$B$_{\mathrm{25}}$ maintained amorphous under the He ion irradiation, till the fluence was up to 1.6×10$^{\mathrm{18}}$ions/cm$^{\mathrm{2\thinspace }}$(69dpa). This indicates that the irradiation resistance of Fe$_{\mathrm{68}}$Zr$_{\mathrm{7}}$B$_{\mathrm{25}}$ is better. After the irradiation, different damage morphologies were exhibited on the surfaces of the two kinds of Fe-based metallic glasses. When the fluence was 1.6×10$^{\mathrm{18}}$ions/cm$^{\mathrm{2}}$, cracks and ductile shear steps appeared on the surface of metallic glass Fe$_{\mathrm{80}}$Si$_{\mathrm{7.43}}$B$_{\mathrm{12.57}}$, and spalling as well as brittle fracture morphology appeared on the surface of metallic glass Fe$_{\mathrm{68}}$Zr$_{\mathrm{7}}$B$_{\mathrm{25}}$. However, blisters and spallings occured on the surface of tungsten at the irradiation fluence of 1×10$^{\mathrm{18}}$ions/cm$^{\mathrm{2}}$, and with the increase of irradiation fluence, the spalling phenomenon became more serious. Thus the irradiation resistance of Fe-based metallic glasses is better than that of tungsten.