Helium irradiation of Ni-(Zr or Nb) metallic glasses: Blistering, flaking and bubble formation

Ni-Zr and Ni-Nb are potential metallic glasses for nuclear applications. We have studied blistering, flaking and bubble formation in Ni64Zr36, Ni33Zr67 and Ni60Nb40 glasses under helium ion bombardment at room temperature. The effect of projectile energy (50-150 keV), total dose (0.01-10 . 1018 ions/cm2), dose rate (10-100 μA/cm2) and thermal crystallization on critical dose for blistering and/or flaking, average blister diameter and development of surface topography was examined. The surface damage effects in metallic glasses were in general similar to those for crystalline materials with the notable exception that the critical dose values are higher by about 50-100% for metallic glasses. TEM investigations revealed irradiation induced partial crystallization of Ni33Zr67 glass. Metallic glasses Ni64Zr36 and Ni60Nb40 were stable under helium irradiation and have also shown very high resistance against blistering and/or flaking. The possible mechanisms of helium trapping in metallic glasses are also discussed. (orig.)