Effects of Bi Inclusion on Tensile Mechanical Property and Deformation Mechanism of Nanopolycrystalline Fe: A Molecular Dynamics study

The effects of bismuth inclusion on the mechanical properties and deformation mechanisms of nanopolycrystalline iron under uniaxial tensile loading were investigated using molecular dynamics simulations. The analysis of the stress-strain behavior of polycrystalline pure Fe and alloy containing Bi inclusion shows that the Young's modulus of the latter is lower, the strain into the yield stage is smaller, and the yield strength is significantly decreased. Microscopic analysis of pure Fe polycrystalline and Fe–Bi polycrystalline systems with small grain size shows that the deformation mechanisms of pure Fe polycrystalline systems are mainly grain boundary migration, grain boundary slip and grain twisting, while a limited amount of twinning can be observed. The deformation of Fe–Bi system is accomplished based on the deformation mechanism of pure Fe system combined with the shear slip of atoms in Bi inclusion and adjacent region. Meanwhile, the nucleation and growth of cavity can be observed inside the inclusion.