NATHANAEL WAGNER SALES MORAIS
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Artigo IPEN-doc 30363 Thermal fatigue of Zircaloyā4 cladded Uā7.5Nbā2.5Zr2024 - MORAIS, NATHANAEL W.S.; MONLEVADE, EDUARDO F.; SCHON, CLAUDIO G.Prototype plates made of U-7.5Nb-2.5Zr alloy, also known as Mulberry alloy, cladded with Zircaloy-4 were thermally fatigued between 200 ĀŗC and 500 ĀŗC investigated. The assembly consisting of a Uranium alloy monolithic core and the Zircaloy-4 cladding was processed by hot rolling and investigated in the āas rolledā state, as well as after applying 9% and 18% reduction in cold rolling. The samples were characterized by Optical microscopy and X-Ray diffraction both before and after the thermal cycling. All samples presented strong volume contraction (shrinkage) in the first thermal cycle, observed concomitantly with the Ī³ ā Ī±" transformation. The relative shrinkage varied with the cold rolling level, being larger for the āas rolledā plate. The failure mechanism observed in all plates was fracture alongside the U-alloy/Zircaloy-4 interface and no transverse crack was observed either in the Zircaloy-4 sheet or in the Uranium core.Artigo IPEN-doc 29909 Microstructural characterization of U-7.5Nb-2.5Zr alloy after ageing and constrained fatigue2023 - MORAIS, NATHANAEL W.S.; MUCSI, CRISTIANO S.; FABRIM, ZACARIAS E.; SCHON, CLAUDIO G.; ROSSI, JESUALDO L.U-7.5Nb-2.5Zr cladded in Zircaloy-4 is one of the most studied fuel prototypes. The Nb and Zrare added to the U to stabilize the body-centered cubic (BCC) gamma phase and grant mechanical and swelling resistance. The U-7.5Nb-2.5Zr undergoes the gamma to Ī±ā²ā² phase transformation, generating compressive stresses due to the volume reduction. The Ī±ā²ā² phase also can transform to a combination of Ī± + Ī³2 phase (equilibrium phases), which are known to be hard and brittle. This work had the objective to test the effect of ageing the gamma to Ī±ā²ā² phase in thermal cycling of a U-7.5Nb-2.5Zr cladded in Zircaloy-4 part. A co-laminated specimen was aged and thermally cycled in a dilatometry experiment. The samples were characterized through X-ray diffraction and metallography. The results show that the gamma to Ī±ā²ā² phase transformations occur at the begin- ning of the initial ageing, followed by stress relief. During the cycling, the sample demonstrated non-equal thermal strains and presented fractures along with the U matrix.