Temperature and composition dependent screw dislocation mobility in austenitic stainless steels from large-scale molecular dynamics

K Chu and ME Foster and RB Sills and XW Zhou and T Zhu and DL McDowell, NPJ COMPUTATIONAL MATERIALS, 6, 179 (2020).

DOI: 10.1038/s41524-020-00452-x

Extensive molecular dynamics simulations are performed to determine screw dislocation mobility in austenitic Fe0.7NixCr0.3-x stainless steels as a function of temperature ranging from 100 to 1300K, resolved shear stress from 30 to 140MPa, and Ni composition from 0.0 to 30.0 at%. These mobility data are fitted to a linear mobility law with a nonzero stress offset, referred to as the threshold stress. We find that both the linear drag coefficient and the threshold stress increase with Ni composition. The drag coefficient increases with temperature, whereas the threshold stress decreases with temperature. Based on these calculations, we determine fitting functions for the linear solute drag coefficient as a function of temperature and composition. The mobility laws determined in this study may serve to inform dislocation dynamics simulations pertinent to dislocation network evolution at elevated temperatures for a wide composition range of austenitic stainless steels.

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