Hydride is a common defect caused by the reaction of zirconium water with primary coolant in the normal operation of zirconium alloy clad tubes in nuclear power plants.

This study aims to study the effect of hydride on mechanical properties of zirconium alloy.

In this study, molecular dynamics method and third-generation charge-optimized many-body (COMB3) potential function were used. Firstly, the molecular dynamics software large-scale atomic/molecular massively parallel simulator (LAMMPS) was used to construct zirconium base models containing different hydrides. Relaxation was performed at 300 K for 50 ps. Then uniaxial stretching was performed at a strain rate of 10¹⁰ s^-1 in the direction [0001] for 30 ps, which was 30% strain.

The results show that the yield strength, strain and Young's modulus of the alloy decrease with the increase of hydride density in the range of 0~1 078 μg·g^-1. When the hydride density is between 1 078 μg·g^-1 and 2 311 μg·g^-1, the yield strength, strain and Young's modulus increase with the increase of hydride density. When the hydride density is 1 078 μg·g^-1, the yield stress of the model drops to the lowest value of 7.69 GPa, which is 42.22% lower than that of the pure Zr model. The yield strain decreases to the lowest value 0.089 5, which is 39.34% lower than that of the pure Zr model. Young's modulus drops to the lowest value of 112.18 GPa, which is 8.94% lower than that of the pure Zr model.

When the hydride density is in the range of 0~1 078 μg·g^-1, in the elastic stage, the increase of hydride density increases the stress concentration area, which is conducive to dislocation nucleation. In the plastic deformation stage, with the increase of hydride density, the initial dislocation is more inclined to expand around the hydride. When the hydride density is in the range of 1 078 μg·g^-1 to 2 311 μg·g^-1, a large number of dislocations are generated due to the high hydride density, resulting in dislocation plugging.