CONICET | Buscador de Institutos y Recursos Humanos

Zr based alloys are widely used as fuel cladding in nuclear pressurized water reactors for their excellent mechanic properties, irradiation stability and corrosion resistance.Alloyed with Fe, Nb and Sn, Zr is the main element in the Zirlo-type alloys, currently vastly used as structural elements and as containers of burnable elements in nuclear reactors. Although Zr is a major component in this type of alloys, it is most important to know the phase diagrams of their components as best as possible. The further knowledge about the effect of the alloying elements will allow advancing in the understanding of the microstructure of these alloys, on which mechanical properties and corrosion strongly depend.The binary phase diagram of the Fe-Zr system has been studied for a long time by several authors because in the nuclear industry the intermetallic phases formed in this binary system play an important role. However, currently there remain uncertainties and controversies about the Fe23Zr6 intermetallic phase. This compound was described for the first time by Svechnikov and up to now, its existences remains controversial.Later, Stein demonstrated that this phase was an oxygen-stabilized compound based on the observation of the segregation of oxygen in Fe23Zr6. But in last years, some authors insisted that Fe23Zr6 phase was a stable phase in the Fe-Zr system.In this work, several binary and ternary samples, located in the Fe-rich region of the Fe-Zr binary diagram, with different purity raw materials, were manufactured and subjected to prolonged heat treatments at 900-1000-1100-1200°C. Before and after heat treatments the phases present in the alloys were identified by using different complementary characterization techniques (mainly X-ray diffraction and microanalysis techniques). Phase balance boundaries in the region were traced and a discussion about the stability of Fe23Zr6 phase under the experimental conditions is made in the present work.