Effect of swift heavy ion irradiation on Zr ₇₀ Ni ₃₀ binary metallic glass: a positron annihilation study

Abstract The assessment of irradiation effects in metallic glasses is important considering the renewed interest for this class of material for a variety of nuclear applications. The Zr 70 Ni 30 thin films metallic glass (MG) deposited on Si substrate by magnetron sputtering technique were exposed to 93.2MeV 129 Xe 23+ heavy-ion irradiation at room temperature, covering a range of ion fluences from 5×10 12 ionscm −2 to 8×10 13 ionscm −2 . The evolution of the irradiation-induced defects in Zr 70 Ni 30 MG has been investigated using Doppler broadening spectroscopy (DBS) and positron annihilation lifetime spectroscopy (PALS). Three lifetime components were distinguished, indicating the presence of different types of open-volume regions at the atomic scale in thin film. The combined results of both DBS and PALS demonstrated that ion irradiation initially increases the excess free-volume density with a homogeneous distribution up to a fluence of (≤2×10 13 ionscm −2 ). In contrast, with increasing fluence (>2×10 13 ionscm −2 ), a reduction in excess free-volume was found, which could be related to structural relaxation accompanied by modifications in atomic arrangement and defect distribution. Moreover, the correlation between the shape and wing parameters provides a basis to identify the nature of the defects, indicating that the type of defect changes at the higher fluence of 4×10 13 ionscm −2 and 8×10 13 ionscm −2 , which affects the performance of Zr 70 Ni 30 metallic glass after ion irradiation.