This work addresses the impact of radiation damage on the leaching of international simple glass (ISG). Pristine and specimens irradiated with multi-energy Au ions were leached for 82 days at 90 o C in pure water and pH 9 and regularly sampled. Samples leached for 13 and 58 days were characterized using transmission electron microscopy (TEM) to study the microstructure(s) of the alteration layers formed from the radiation-damaged and pristine glasses. Furthermore, a sample altered for 82 days was immersed in water enriched in isotopically tagged water molecules (H2 18 O) to study and compare the mobility and reactivity of water at room temperature in the alteration layers formed on these glasses. The studies revealed that radiation damage diminished the chemical durability of the ISG glass since the beginning of the leaching experiment. Concomitantly, the formation of a non-porous alteration layer of about 237 nm after 13 days of leaching evolving into the formation of a nanoporous alteration layer of about 570 nm after 58 days of leaching was observed in the irradiated glasses. In contrast, a non-porous altered layer of about 138 nm only developed in the non-irradiated specimen altered for 58 days. Using energy-filtered transmission electron microscopy, the altered layers in all the cases were found to be depleted in boron, in agreement with the time of flight secondary ion mass spectroscopy studies. Despite pore formation, similar behaviour in the 18 O - 16 O exchanges (with respect to the uncertainties) was observed in the major part of the alteration layers whether formed from the irradiated or pristine ISG, leading to the conclusion that the greater alterability of the radiationdamaged ISG may not be due to the porosity. However, isotopic exchanges also revealed a significantly higher reactivity of water in the alteration-layer/glass interface for the irradiated glass. While these studies provide important insights about the role of porosity and radiation damages, they also highlight the complex nature of glass dissolution and suggest that studies directed at alteration-layer/glass interface are needed to better understand and explain the mechanisms controlling the glass dissolution in the residual alteration rate regime.

Elemental specific chemical complexity is known to play a critical role in microstructure development in single-phase concentrated solid-solution alloys (SP-CSAs), including both He bubble formation and irradiation-induced void swelling. While cavity formation and evolution under ion irradiation at elevated temperature are complex nonequilibrium processes, chemical effects are revealed at the level of electrons and atoms herein in a simplified picture, using Ni and a special set of Ni-based SP-CSAs composed of 3d transition metals as model alloys. Based on Ni and model alloys with minimized variables (e.g., atomic mass, size, and lattice structure), we discuss the effects of chemically-biased energy dissipation, defect energetics, sluggish diffusion, and atomic transport on cavity formation and evolution under both self-ion Ni irradiation and He implantation. The observed difference in microstructure evolution is attributed to the effects of d electron interactions in their integrated ability to dissipate radiation energy. The demonstrated impact of alloying 3d transition metals with larger differences in the outermost electron counts suggests a simple design strategy of tuning defect properties for improved radiation tolerance in structural alloys.

No abstract

The stability of the face-centred cubic austenite (γ-Fe) phase in a commercial stainless steel (AISI-348) was investigated through in situ transmission electron microscopy (TEM) with heavy ion irradiation at 1073 K up to a fluence of 1.3×10 17 ions•cm −2 (corresponding to a dose of 46 dpa). The γ-Fe phase was observed to decompose at a fluence of around 7.8×10 15 ions•cm −2 (3 dpa) when a new phase nucleated and grew upon increasing irradiation dose. Scanning transmission electron microscopy (STEM) with energy dispersive X-ray (EDX) spectroscopy and multivariate statistical analysis (MVSA) were used to characterise the irradiated specimens. The combination of such experimental techniques with calculated equilibrium phase diagrams using the CALPHAD method led to the conclusion that the new phase formed upon irradiation is the body-centred cubic Cr-rich α phase. At the nanoscale, precipitation of M 23 C 6 (τ-carbide) was also observed. The results indicate that ion irradiation can assist the austenitic stainless steel to reach a non-equilibrium state similar to a calculated equilibrium state observed at lower temperatures in which, under conventional conditions, is suppressed due to kinetic restrictions.

No abstract