Abstract: U-50%Zr alloy for nuclear fuel was prepared by high-frequency induction melting, and its microstructure and phase constituent were analyzed using metallographic microscope and X-ray diffractometer. The Gleeble-3800 thermal simulation test machine was used to conduct hot compression tests at different deformation temperatures (500, 550 and 600 ℃) and strain rates (0.01 s, 0.1 and 1 s^-1) to investigate its hot deformation behavior. The results show that, except for a deformation temperature of 600 ℃ and a strain rate of 0.01 s^-1, the U-50%Zr alloy exhibits significant work hardening characteristics under other deformation conditions. At the same strain rate, the peak stress decreases with the increase of deformation temperature, especially at 600 ℃, where the peak stress decreases significantly compared to 500 ℃ and 550 ℃. At the same deformation temperature, the peak stress increases with the increase of strain rate. After hot deformation, no phase transformation occurs in the microstructure, all of which are δ-UZr₂ phase. As the hot deformation temperature increases, the grain size of the alloy initially remains basically unchanged and then increases. At 500 ℃ and 550 ℃, the grain size is around 250 μm, and at 600 ℃, the grain size significantly increases to 493 μm. Based on peak stress, the constitutive equation of U-50%Zr alloy is established using the hyperbolic sine function Arrhenius model and temperature compensation factor Z parameter, with a hot deformation activation energy Q=694.9 kJ/mol. A hot working map is constructed using DMM dynamic material model, and the appropriate processing range is determined as follows: deformation temperature above 540 ℃, strain rate between 0.01 s^-1 and 1 s^-1.

Key words: nuclear fuel U-50%Zr alloy, hot compression deformation, constitutive equation, hot working map, microstructure