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Influence of Zirconium Alloy Chemical Composition on Microstructure Formation and Irradiation Induced Growth
Shishov VN, Peregud MM, Nikulina AV, Shebaldov PV, Tselischev AV, Novoselov AE, Kobylyansky GP, Ostrovsky ZE, Shamardin VK


Pages: 22    Published: Jan 2002


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Source: STP1423-EB


Abstract
The studies of the dislocation structure, phase, and microchemical compositions of alloy Zr-1Nb-1.2Sn-0.35Fe (E635) and its modifications containing Fe from 0.15 to 0.65% were carried out before and after research reactor irradiation at 350°C to maximal fluence of 10 m (E > 0.1 MeV) and at 60°C. The size and concentration of the -type loops depend on the alloy composition and fluence and saturate even at low doses (<1 dpa). The evolution of the -component dislocation structure in recrystallized alloys of E365 type is determined by the chemical and phase compositions of alloys specifically, by the Fe/Nb ratio and the threshold dose, and is consistent with the irradiation growth strain acceleration. In E635 alloy containing 0.15%Fe the accelerated growth is observed after the dose of 15 dpa and is attended with the evolution of the dislocation structure which is similar to Zr-1Nb (E110) alloy behavior. The irradiation induced growth of E635 type alloy containing 0.65% Fe is similar to that of E635 having the normal composition; no dislocations are observed up to the dose of 20 dpa. E635 alloy contains precipitates Zr(NbFe) (HCP) as the basic excess phase and individual (Zr,Nb)Fe (FCC) precipitates; in 0.15%Fe alloy aside from Zr(Nb,Fe) also -Nb (BCC) particles precipitate, while 0.65%Fe alloy contains Zr(Nb,Fe) and (Zr,Nb)Fe particles. Irradiation at 330 350 °C does not effect an amorphization of -Nb or Zr(Nb,Fe) precipitates; however, at higher fluences the -Nb phase becomes depleted in Nb and Zr(Nb,Fe) in Fe. Irradiation at 60° leads to the amorphization of Zr(Nb,Fe) in E635. The analysis revealed that the key factors promoting a delay in the accelerated irradiation growth in Zr-Nb-Fe-Sn alloys are the composition of (Nb,Fe,Sn) solid solution and the Fe/Nb ratio in alloys.


Keywords:
zirconium alloys, irradiation growth, electron microscopy, dislocation, microstructure, precipitates, composition, fluence

Paper ID: STP11415S
Committee/Subcommittee: B10.02
DOI: 10.1520/STP11415S
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