Structural evolution features of the 42XNM alloy during neutron irradiation under VVER conditions

The impact of helium ion irradiation on the evolution of microstructure and mechanical properties of a Ni-45%Cr-1.4%Mo (wt.%) alloy has been investigated. Analysis via transmission electron microscopy (TEM) of a pristine sample revealed an uneven distribution of alpha-Cr phase precipitates along with a few isolated planar arrangements of dislocations within the fcc γ-Ni matrix phase. A detailed study of irradiated samples established the presence of radiation-induced defect clusters, dislocation loops, network dislocations and He-stabilized voids as perceptible irradiation effects. Furthermore, examination of the irradiated sample revealed nearly complete dissolution of the native alpha-Cr precipitates, accompanied by a simultaneous increase in the Cr and Mo content of the matrix. X-ray diffraction (XRD) and positron annihilation spectroscopy (PAS) studies also confirmed lattice swelling as an effect of irradiation in this alloy, likely caused by helium-stabilized voids. A line profile analysis method which takes into account of planar defects, was employed on GIXRD (Grazing Incidence X-ray Diffraction) data to analyze changes in microstructural parameters such as domain size, microstrain, dislocation density, and lattice parameter as a function of irradiation dose. All of these irradiation-damage manifestations led to the increase in the hardness of the alloy in nano-indentation experiment. Overall, the findings of this work provide significant insights into the radiation-induced microstructural changes and their effect on the hardening behavior of the studied Ni-Cr-Mo alloy.

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Stability of the Y–Ti–O oxides in reactor materials under neutron irradiation at high temperatures

Фролов

Кулешова

Гурович

et al. 2022

Vopr. materialoved.

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The paper presents the results of electron microscopic studies of ferrite-martensitic steel samples hardened with Y-O oxides, EP-450 DUO in the initial state and after neutron irradiation in the BN-600 reactor at 1000°C to a damaging dose of 77.5 dpa. These studies showed that the main types of oxide phases were Y2(Si, Ti)2O7 and Y2(Si, Ti)O5. These precipitates at sizes less than 10-20 nm were semi-coherent with a ferritic matrix of steel EP-450 DUO with the ratio (110)malrix//(221)palticle. Some of the Y-Ti-O oxides in the initial state were Y2Ti2O7-type with some deviations from the stoichiometric composition.However, after neutron irradiation under BN-600 conditions at temperature ~ 1000°C, oxide particles could not be described by the indicated stoichiometry. Besides, after irradiation, silicon and aluminum were found in the oxide's composition. In the case of taking these elements into account during the construction of a triple composition diagram, it was shown that the oxide phases had Y2(Ti, Si, Al)2O7 and Y2(Ti, Si, Al)O5 types. It was established that in samples of EP-450 DUO steel in the initial state with oxide particles up to 20 nm in size, the yttrium content is generally lower than the titanium concentration. The titanium and yttrium concentrations corresponded to the stoichiometric composition Y2Ti2O7 (1:1) with a further increase in the average diameter of these phases. After irradiation, the situation changed somewhat: the yttrium content in most oxide phases exceeds the total concentration of titanium, silicon, and aluminum.The paper also presents the analysis of porosity and evolution of grain structure in EP-450 DUO steel after neutron irradiation.

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Structural evolution features of the 42XNM alloy during neutron irradiation under VVER conditions

Cited by 5 publications

References 64 publications

Microstructural evolution of the 42XNM alloy during a severe accident (LOCA)

Microstructural evolution of the 42XNM alloy during a severe accident (LOCA)

Understanding the Impact of He Ion Irradiation on the Microstructure and Mechanical Properties of a Ni-Cr-Mo Alloy: A Comprehensive Study

Stability of the Y–Ti–O oxides in reactor materials under neutron irradiation at high temperatures

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