Influence of dilute impurities on the evolution of defect cascades in nickel

Abstract

We have employed transmission electron microscopy to study the formation of vacancy dislocation loops from defect cascades produced by a 50 keV Kr + ion irradiation of Ni and its dilute alloys with Si and AI. An unusual and reproducible dependence of the loop collapse probabilities and loop size distributions on solute content was found. The results are explained by impurity caused changes in both the collisional and thermal spike (molten zone) phase of the defect cascade. Specific mechanisms include disruption of focussons by impurities to change the energy density profile within the collision cascade, interruption of replacement collision sequences, and interstitial trapping to reduce recombination during the thermal spike phase. Applying these mechanisms to a statistical distribution of the spatial extent of cascades and to the melt-zones, ali the experimental observations can be explained.

Investigation of defect clusters in ion-irradiated Ni and NiCo using diffuse X-ray scattering and electron microscopy

“…Analogous cross sections for interstitial loops are not shown because they look very similar to those of vacancy loops mirrored about q = 0 [12]. We considered only faulted loops because most work shows that they are more common than perfect loops in nickel [30,31,32,33,34]. Spectra are shown for different vacancy type defects of similar size.…”