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In situ irradiation in transmission electron microscope following pre-irradiation was performed on Fe-0.6Ni alloy to investigate the growth of dislocation loops under irradiation. The observations showed two types of loop growth behaviour. One type was almost linear growth with irradiation dose, possibly caused by loop absorbing freely migrating defects. The other was abrupt growth with rapid increase in diameter. It was found that nanometre-sized loop might migrate one-dimensionally, following which the large loop could absorb the small loop. This process can result in the abrupt growth of loop and broadening of loop size distribution. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The microstructure and nanomechanical properties of three samples of the modified stainless steel (referred as the alloy D9) were systematically characterized after neutron irradiation in the Advanced Test Reactor. The samples were irradiated to 5.0, 8.2, and 9.2 displacements per atom at 448, 430, and 683°C, respectively. The evolutions of dislocation loops, cavities, and radiation-induced precipitates were quantitatively studied to reveal their dose and temperature dependencies. Nanohardness and nanoindentation creep tests were conducted at room temperature on the irradiated samples. Unexpected radiation hardening was observed in the highest-temperature-irradiated sample due to the formation of an unknown type of Ni- and Si-rich precipitates whose contributions to the radiation and mechanical performances of the alloy were discussed. We provide the radiation-microstructure-property correlations of alloy D9 with new insights, which can benefit the development and optimization of advanced austenitic alloys for future nuclear applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this study, APT and TEM analyses were used to characterise two Zr-based alloys neutron-irradiated to 13.7 dpa. The high spatial and chemical resolution of these techniques has enabled the irradiation-induced nanoscale distribution of solute elements to be characterised. The results on both Zircaloy-2 and low-Sn ZIRLO support previous observations of Fe segregation to planar dislocation arrays with enhanced Sn between. In Zircaloy-2, the APT data in this study have also revealed short-range (∼2 nm) clustering of Fe and Sn atoms both within the Fe-enriched planes and in the regions between dislocation arrays. The resultant microstructure is reminiscent of spinodal decomposition. In low-Sn ZIRLO Nb-rich precipitates formed in the Sn-rich planes. The data in this article enhance our understanding of microstructural evolution in Zr alloys under neutron irradiation and are relevant for predicting changes in the properties of Zr alloys in-service in fission reactors. [Display omitted] [ABSTRACT FROM AUTHOR]