Au and Ag ion irradiation effects on the carbide precipitation and Ar bubble formation in solubilized AISI 316L alloys

Abstract

This contribution reports on transmission electron microscopy observations of Au and Ag ion irradiated complex metal alloys obtained by solution annealing treatments in AISI 316L foils. Two sets of samples are used: i) pristine solution annealed ones, and ii) solution annealed samples implanted with Ar to form a dense array of small bubbles located in a 250 nm thick surface layer. The irradiations were done in samples kept at 550 °C using 5 MeV Au and 3.5 MeV Ag accelerated ions and fluences calculated to produce damage levels equivalent to 20 and 40 dpa. The results obtained demonstrate that the irradiations cause the formation of 7 times larger cavities in the pristine samples and bubble enlargement 30% superior in Ar contained samples for Au ions as compared to the Ag case. This means that Au irradiations produce a larger number of excess vacancies than Ag at the same dpa values. This phenomenon is discussed in terms of the point defect densities produced by individual ion induced displacement cascades. In addition, for Au irradiations, we observe the formation of MC phase carbide precipitation only in samples containing Ar bubbles. This effect is discussed considering that the nucleation kinetic of the MC precipitates can be controlled by vacancy supersaturation.