2024, 45(S2): 245-253.
doi: 10.13832/j.jnpe.2024.S2.0245
Abstract:
The grain of the SiC layer of tristructural-isotropic (TRISO) particles will undergo phase transformation, fracture and abnormal growth after irradiation and high temperature test. The mechanical behavior of these SiC layers is very important for the safety study of TRISO particles. In this paper, molecular dynamics simulation is used to study the nanomechanical behavior and properties of SiC layer. Four typical SiC layer structures are constructed according to the experimental phenomena: 3C-SiC before service, 3C-SiC after irradiation test, 6H-SiC after high temperature test, and 6H/3C-SiC after high temperature & irradiation test. The nanomechanical behavior and mechanical properties of SiC layer are analyzed by load-depth curve, dislocation evolution, stress & strain, and atomic diffusion. The results show that the SiC layer after service has less interaction between dislocations during the nanoindentation loading process, which reduces the plastic deformation, resulting a decrease in Young's modulus. For the SiC layer after irradiation test and high temperature & irradiation test, the concentration degree of stress and strain directly below the indenter decreases, and the transverse distribution of stress, strain, and atomic diffusion increases, resulting in a decrease in hardness. For the SiC layer after high temperature test, the concentration degree of stress and strain directly below the indenter increases, and the vertical distribution of stress, strain, and atomic diffusion increases, resulting in an increase in hardness. The research results give a quantitative explanation for the mechanical behavior and properties of various types of SiC layers, which is helpful to understand the relationship among the microstructure, mechanical behavior and mechanical properties of SiC layers.
