X-ray diffraction analysis of secondary phases in zirconium alloys before and after neutron irradiation at the MARS synchrotron radiation beamline

作者：Bechade J L^*; Menut D; Doriot S; Schlutig S; Sitaud B

来源：Journal of Nuclear Materials, 2013, 437(1-3): 365-372.

DOI：10.1016/j.jnucmat.2013.02.020

To further advance understanding of microstructural evolution in zirconium alloys for high burnup applications in PWR, it is important to obtain precise characterizations of second-phase particles present in the bulk alloys as a function of the neutron-irradiation fluence.
X-ray diffraction from a synchrotron radiation source (SOLEIL) was used to identify and follow the evolution of second-phase particles that are in very small volume fractions in two zirconium alloys: Zy-4 in stress-relieved metallurgical state before irradiation and Zr-1%Nb (MS (R)) in recrystallized metallurgical state before and after neutron irradiation. Despite the fact the neutron irradiated sample is not in the as-irradiated state due to a thermal treatment and creep test performed after irradiation, interesting results have been obtained on secondary phases using XRD techniques.
Analyses have been performed at the MARS beamline, fully dedicated to advanced structural and chemical characterizations of radioactive matter.
A first proof of the improvement brought by these new analyses performed at the MARS beamline is given with Zr(Fe, Cr)(2) precipitates found in unirradiated Zy-4 alloy in stress relieved metallurgical state, highly textured and displaying significant residual stresses and numerous dislocations: lattice parameters, crystallite size and microstrains (line profile analysis using the Williamson-Hall method after correction for instrumental broadening) have been estimated with very good accuracy.
Then, second phase particles of the Zr-1%Nb alloy (M5 (R)) have been analyzed before and after irradiation. For the Zr(Fe, Nb)(2) Laves phase, the diffraction line disappeared after neutron irradiation. For beta-Nb phases, the evolution of diffraction peaks clearly show the convolution of two phenomena: in one hand slight decreases in Nb content for native beta-Nb particles and on the other hand irradiation-enhanced precipitation of nano-sized needle-like beta-Nb particles. To our knowledge, this is the first time that the crystallographic unit cell, lattice parameter and Nb content of the beta-Nb irradiation-enhanced precipitates have been determined using synchrotron radiation on irradiated Zr-1%Nb (M5 (R)) alloy.

• 出版日期2013-6
• 单位中国地震局