Cryo-rolling enhanced inhomogeneous deformation and recrystallization grain growth of a zirconium alloy

This work focuses on the influence of cryo-rolling on subsequent recrystallization of hexagonal Zr-4 alloy. With initial recrystallized microstructure, the as-received Zr-4 sheets were rolled at liquid nitrogen temperature (LNT) and room temperature (RT). For each rolling temperature, two levels of strain, 20% and 40%, were applied. Then, samples, including as-received and rolled sheets, were annealed at 700 °C for 3 min-5 min. Microstructures of the deformed and annealed Zr-4 samples were characterized in detail by electron backscatter diffraction (EBSD) method. After rolling, no twin lamella is observed in Zr-4 sample. It is found that the intensity of the heterogeneous deformation in cryo-rolling is more severe than that in RT-rolling. After annealing, the recrystallized average grain size of Zr-4 decreases with the increases of the applied strain at both deformation temperatures. For a given rolling reduction, the recrystallized average grain size increases with decreasing deformation temperature. The texture orientation of Zr-4 was not remarkably changed during the rolling deformation and annealing process.