Varying Diffusion Kinetics Along Random Grain Boundaries in a Model Austenitic Stainless Steel

Molecular Dynamics simulations of the diffusion process along a grain boundary in a model austenitic stainless steel are presented. We address diffusion in a series of general grain boundaries of tilt character with random misorientations around the axis. The diffusion process is quantified by analyzing individual atomic displacements. The results of simulations are verified by comparison with available experimental data. The results show that Cr diffuses about 25 pct faster than Fe or Ni. Most importantly, the simulations show that the diffusion kinetics varies widely among the set of general high angle boundaries studied, with diffusivities that span more than an order of magnitude. The variation is analyzed for correlations with grain boundary structure and energy. Faster diffusion kinetics are associated with higher energy grain boundaries and boundaries that are narrower, with more extra volume and are less centrosymmetric in their structure.

Automated summary

Molecular Dynamics simulations were used to study the diffusion process along a grain boundary in a model austenitic stainless steel. The results showed that Cr diffuses about 25 percent faster than Fe or Ni, and the diffusion kinetics varied widely among different general high angle boundaries. Faster diffusion kinetics were associated with higher energy grain boundaries and narrower boundaries with more extra volume and less centrosymmetric structure.