Novel α + β Zr Alloys with Enhanced Strength

Abstract

Low-alloyed zirconium alloys are widely used in nuclear applications due to their low neutron absorption cross-section. These alloys, however, suffer from limited strength. Well-established guidelines for the development of Ti alloys were applied to design new two-phase ternary Zr alloys with improved mechanical properties. Zr-4Sn-4Nb and Zr-8Sn-4Nb alloys have been manufactured by vacuum arc melting, thermo-mechanically processed by annealing, forging, and aging to various microstructural conditions and thoroughly characterized. Detailed Scanning electron microscopy (SEM) analysis showed that the microstructural response of the alloys is rather similar to alpha + beta Ti alloys. Duplex microstructure containing primary alpha phase particles surrounded by lamellar alpha + beta microstructure can be achieved by thermal processing. Mechanical properties strongly depend on the previous treatment. Ultimate tensile strength exceeding 700 MPa was achieved exceeding the strength of commercial Zr alloys for nuclear applications by more than 50%. Such an improvement in strength more than compensates for the increased neutron absorption cross-section. This study aims to exploit the potential of alpha + beta Zr alloys for nuclear applications.

The Effect of Cooling Rate on Crystallographic Features of Phase Transformations in Zr-2.5Nb

“…In general, the obtained results of the microstructure characteristics align with the findings from [ 14 , 25 , 26 ]. Some discrepancies, such as differences in alloy chemical compositions, may be attributed to the variation in experimental conditions [ 14 , 26 ], such as the superheating temperature during ST [ 25 ] and annealing in the capsule [ 14 , 25 ].…”

“…In general, the obtained results of the microstructure characteristics align with the findings from [ 14 , 25 , 26 ]. Some discrepancies, such as differences in alloy chemical compositions, may be attributed to the variation in experimental conditions [ 14 , 26 ], such as the superheating temperature during ST [ 25 ] and annealing in the capsule [ 14 , 25 ]. These factors influence both the actual cooling rates and the critical cooling rates, which affect the kinetics of the transformation processes and the size and morphology of the α(α′)-phase crystallites.…”

“…Manufacturing zirconium alloy components for nuclear reactors involves numerous thermomechanical treatments, with the resulting microstructure determining the product’s long-term and short-term properties [ 13 ]. The microstructure of Zr alloys, including local and integral texture states, crucially affects functional properties, prompting research into obtaining various microstructures through heat treatments, primarily by altering cooling rates from the β-region [ 14 , 25 , 26 ].…”

“…In [ 26 ], the microstructures of the novel Zr-4Sn-4Nb and Zr-8Sn-4Nb alloys are highlighted for their similarity to the microstructures of (α + β) titanium alloys. The potential for tailoring microstructures through heat treatment processes is also demonstrated.…”