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

D Farkas, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 52, 1117-1126 (2021).

DOI: 10.1007/s11661-021-06151-6

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.

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