Processing maps and microstructural characterization of typical regions during hot deformation of N36 zirconium alloy

Hot compression tests were performed on N36 zirconium alloy at 620-770 °C and strain rates of 0.01-10 s -1 to elucidate its hot deformation behavior and microstructural evolution. A strain-compensated Arrhenius constitutive model was established with high predictive accuracy, and processing maps based on the dynamic materials model identified an optimal processing window of 720-770 °C/0.01-0.05 s -1 at a true strain of 0.9. Electron backscatter diffraction (EBSD) revealed temperature and rate-dependent mechanisms. At 620 °C, lamellar α phases with high dislocation density dominated, and deformation was governed by dynamic recovery (DRV); at 5 s -1 , the power dissipation coefficient η fell to 0.073, suggesting a high susceptibility to crack initiation. At 670 °C, spheroidization of lamellar α at low strain rates promoted homogeneity and the onset of dynamic recrystallization (DRX). Between 720 and 770 °C, the alloy exhibited fully spheroidized grains and a high fraction of recrystallized microstructure at low strain rates. Strain rate strongly affected DRX. At 720 °C, increasing the strain rate from 0.01 to 1 s -1 reduced high-angle grain boundaries by 28.1% and raised the kernel average misorientation value from 0.36° to 1.33°, indicating suppressed recrystallization and enhanced dislocation accumulation. These findings provide insights into the deformation mechanisms of N36 alloy and offer guidance for optimizing its use in nuclear fuel cladding.