Revealing the influence of temperature, pressure, and grain size on nitrogen diffusion and the strength of titanium: a molecular dynamics study

Molecular dynamics (MD) simulations utilising the 2NN-MEAM potential were conducted to explore nitrogen diffusion in polycrystalline titanium. The MD simulations demonstrated that nitrogen diffusion in titanium is strongly influenced by temperature and grain size, with a less pronounced effect of pressure. Simulation results indicate a decrease in the strength of nitrogen-impregnated titanium at elevated temperatures, despite the increased diffusion and penetration of nitrogen atoms into the titanium lattice as the temperature increases. Increased temperature enhances atomic vibrations, facilitating dislocation motion and consequently reducing the strength of nitrogen-impregnated titanium. Increasing the grain size of nitrogen-impregnated titanium reduced the number of grain boundaries, which serve as pathways for the rapid diffusion of nitrogen atoms. Although pressure had a minimal impact on diffusion, it significantly increased the material's tensile strength. This strengthening effect is attributed to increased material density and the suppression of vacancies. These findings offer valuable insights for optimising nitriding processes to achieve tailored material properties suitable for diverse industrial applications.