A dual-phase strain-transformable zirconium alloy with exceptional yield strength (1.2 GPa) and low elastic modulus (70 GPa) via TWIP and phase reversion

The present study focuses on the development of a novel Zr-12Nb-3Sn alloy displaying a body-centered tetragonal (BCT) / β dual-phase microstructure and engineered to achieve a superior combination of high strength and low elastic modulus. The BCT phase is shown to play a critical role in enhancing strength without increasing elastic modulus. Comprehensive analyses using in situ straining electron backscatter diffraction (EBSD) experiment and transmission electron microscopy (TEM) were conducted to characterize the microstructure of the BCT phase and the associated deformation mechanisms, including dislocation slip, stress-induced reversion from BCT to β transformation, and mechanical twinning. The present findings reveal that the BCT phase and mechanical twinning both contribute to material strengthening, whereas the stress-induced reversion of the BCT phase to β acts as a mechanism for stress relaxation. As a result, the alloy demonstrates exceptional mechanical performance, achieving a yield strength exceeding 1200 MPa, an elastic modulus of approximately 70 GPa, and an elongation of ~13%.