Molecular dynamics study of the effect of hydrogen on the diffusion and tensile of polycrystal Fe with void defect

Abstract

The diffusion of hydrogen in polycrystal iron with/without void defect and the effects of hydrogen and void on the uniaxial tensile properties of polycrystal iron under different conditions were studied by molecular dynamics simulation method. The research results indicate that the diffusion coefficient of hydrogen in a model with a diameter of 30 Å void is 0.81 * 10 −5 𝑐𝑚 2 /𝑠 at 300 K and hydrogen content is 0.5%, while it is 0.7 * 10 −5 𝑐𝑚 2 /𝑠 without void. The void increases the diffusion rate of hydrogen by 15.7% under the same conditions. The tensile simulation results show that void and hydrogen reduce the tensile strength. The tensile strength without hydrogen and void is 6.7 GPa, 6.2 GPa with void, and 6.02 Gpa with 1% hydrogen and void. The two conditions reduce the tensile strength by 7.46% and 10.15% respectively. In addition, the influence of tensile rate is also studied. At high tensile rate (0.006~0.012/ps), the tensile rate of 0.012/ps was 8% higher than the 0.006/ps. This study provides important simulation data and scientific basis for the hydrogen embrittlement and void defect of nanograined Fe.