Microstructural characterization of U-7.5Nb-2.5Zr alloy after ageing and constrained fatigue

U-7.5Nb-2.5Zr cladded in Zircaloy-4 is one of the most studied fuel prototypes. The Nb and Zr are added to U stabilize body-centered cubic (BCC) gamma phase grant mechanical swelling resistance. undergoes α′′ transformation, generating compressive stresses due volume reduction. also can transform a combination α + γ2 (equilibrium phases), which known be hard brittle. This work had objective test effect ageing thermal cycling part. A co-laminated specimen was aged thermally cycled dilatometry experiment. samples were characterized through X-ray diffraction metallography. results show that transformations occur at begin- ning initial ageing, followed by stress relief. During cycling, sample demonstrated non-equal strains presented fractures along with matrix.