Molecular Dynamics-based Study of Effect of Porosity on Crack Propagation at FeO/Fe Interface

Porosity is an important factor affecting the crack extension at the interface between oxide and steel matrix. In this paper, two models including Model I (fixed pore defect number model) and Model II (fixed pore defect size model), were established by the molecular dynamics simulation software LAMMPS, and the effect of porosity on the crack extension at the interface was investigated in terms of tensile strength, centrosymmetry parameter (CSP) analysis and local stress distribution at the interface. The results show that the tensile strength of model II is lower than that of model I at the same porosity, indicating that the range of pore defect distribution has more influence on the tensile strength of the material than the size of pore defects. Meanwhile, the dynamic instability during crack expansion leads to asymmetric crack expansion, and the increase of porosity will hinder the stress growth and crack expansion rate and enhance the asymmetry of crack expansion. When the porosity reaches to 9%, after the interface crack extension, the + x direction crack tip in model I deflects the pore defects above the interface, and the upper square pore defects in model II shows the fusion development after the interface crack extension.