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A dual-phase 12Cr oxide-dispersion-strengthened (ODS) alloy, with improved corrosion and oxidation resistance exhibits promising void swelling resistance and microstructural stability under Fe 2+ ion irradiation to 800 dpa at 475 ∘C. Dispersoids were originally present in both ferrite and tempered martensite grains, with the latter having a wider range of dispersoid sizes. In both phases dispersoids> 10 nm in diameter are incoherent with the matrix, while smaller dispersoids are coherent. During irradiation the larger incoherent dispersoids shrank and disappeared. Beyond 60 dpadispersoids in both phases approached a near-identical equilibrium size of ~2-2.5 nm, which appears to be rather independent of local displacement rate. Grain morphology was found to be stable under irradiation. Compared to other ferritic-martensitic alloys, the ion-induced swelling of this alloy is quite low, arising from swelling resistance associated with both tempered martensite and dispersoids in both phases, with the swelling in tempered martensite being an order of magnitude less than in the ferrite phase.

a b s t r a c tIn this study, the microstructure of a 12Cr ferritic-martensitic oxide-dispersion-strengthened (ODS) alloy is studied before and after Fe ion irradiation up to 200 peak displacements per atom (dpa). Irradiation temperature ranges from 325 to 625 C. Before irradiation, both coherent and incoherent dispersoids exist in the matrix. In response to irradiation, the mean sizes of dispersoids in both the ferrite and tempered martensite phases change to equilibrium values that increase with irradiation temperature. The evolution of dispersoids under irradiation is explained by a competition between athermalradiation-driven shrinkage and thermal-diffusion-driven growth, with interface coherency affecting the growth mechanism. However, each coherency type exhibits different evolution behavior under irradiation. Coherent dispersoids, regardless of their initial size, change toward an equilibrium size at each temperature tested. On the other hand, incoherent dispersoids are destroyed at lower test temperatures but survive while shrinking in size at higher temperatures. This difference in behavior can be explained by the lower interfacial energy of coherent dispersoids in comparison with incoherent dispersoids. This study sheds light on the roles of interface configurations in maintaining dispersoid integrity under irradiation.

2016-11-02T18:49:00

Gamma-phase lithium aluminate (-LiAlO 2 ) is a breeder material for tritium, a necessary substance for strategic stockpile and fusion power systems. A fundamental study of structural evolution and tritium diffusion in -LiAlO 2 under displacive irradiation is needed to fully assess the material performance. This study utilizes ion implantation of protium (surrogate for tritium) and helium in -LiAlO 2 single crystals at elevated temperatures to emulate the irradiation effects. The results show that at 573 K there are two distinct disorder saturation stages to 1 dpa without full amorphization; overlapping implantation of H 2 + and He + ions suggests possible formation of gas bubbles. For irradiation to 10 21 H + /m 2 (0.36 dpa at peak) at 773 K, amorphization occurs at surface with H diffusion and dramatic Li loss; the microstructure contains bubbles and cubic LiAl 5 O 8 precipitates with sizes up to 200 nm or larger. In addition, significant H diffusion and release are observed during thermal annealing.