Heavy-ion irradiation of nickel and nickel alloys

Abstract

The radiation damage produced by low-dose 80 keV Ni⁺ and W⁺ heavy-ion bombardment of Ni, Ni/Cr 8%, Ni/Cr 17%, Fe/Ni 10%/Cr 17% and a 321 austenitic stainless steel has been studied by means of transmission electron microscopy. In all materials small vacancy loops were observed, produced heterogeneously by the collapse of displacement cascades. Loop numbers and sizes have been measured, and geometries analysed. A progressive reduction in the defect yields in the alloys, which is not accompanied by a change in the distribution of defect sizes, is interpreted tentatively in terms of impurities causing a reduction in the probability of loop nucleation.

The temperature dependence of the defect yield in the temperature range from room temperature to 500°C has been investigated in Ni and Ni/Cr 17% irradiated with 80 keV W²⁺ ions. In Ni the results are consistent with an athermal cascade collapse process which is followed by loop shrinkage due to thermal emission of vacancies: this results in a sharp decrease in the measured yield at 500°C compared to lower temperatures. This sharp decrease is not observed in the Ni/Cr 17% alloy, indicating that loop lifetimes in the Ni/Cr 17% alloy at 500°C are at least an order of magnitude longer than in Ni.