RIAR JSC, Dimitrovgrad, Russia:

A. V. Obukhov, Senior Researcher at the Department of Reactor Materials Science, Candidate of Technical Sciences, e-mail: micron1803@mail.ru
G. P. Kobylyanskiy, Lead Researcher at the Department of Reactor Materials Science, Doctor of Technical Sciences, e-mail: gpk@niiar.ru

Using transmission electron microscopy, the authors of this paper looked at the effect of reactor irradiation in the temperature ranges of 40 to 70 and 290 to 340 ^oC on the elemental composition, crystal structure and particle sizes of the second phases in zirconium alloys E110 and E635. Regularities have been established behind redistribution of elements between the second phase particles and the solid solution of the surrounding matrix in the above alloys as a function of a rising dose and a changing irradiation temperature. The authors note that the redistribution of elements between the structural components of the above zirconium alloys follows a similar pattern in both the experimental reactor BOR-60 and the power reactor VVER-1000. A difference is shown in the effect produced by irradiation on the morphology and elemental composition of β-Nb phase and Laves phase precipitates in the above zirconium alloys in the low temperature region of 40 to 70 ^oC and in the temperature range of 290 to 340 ^oC. It is noted that the Laves phase particles become amorphous as the result of low-temperature irradiation, whereas the β-Nb particles retain their BCC structure. The authors offer their interpretation with regard to the staged transformation of the Laves phase HCP monocrystal structure into the BCC polycrystal structure induced by rising irradiation dose. The role of iron is shown as it leaves the Laves phase and enters the surrounding matrix during crystal lattice transformation. The paper describes stages when fine dispersed irradiation-induced particles appear in alloys E110 and E635 and when they change their size and concentration as the irradiation dose keeps rising. The difference between the particles are also noted in the said alloys.

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