Atomic insights on interaction mechanism of dislocation with void/impurity/ precipitates in bcc iron

Ferritic steels are important cladding and structural material for current and advanced reactors containing Fe as a primary compositional matrix element. Three proposed models containing voids, impurity P, and nano oxides embedded in Fe were simulated using molecular dynamics code LAMMPS. The interaction mechanism of dislocation for each model was observed and compared by analyzing its strengthening effect through the stress-strain curve. In considering the interaction of dislocation with voids, it was observed that for all void sizes, dislocation bypass voids following orowan unpinning mechanism without any loop irrespective of any radii, while for P clusters, dislocation is trapped at the interface and leaves it after making a screw dipole shape following orowan mechanism. Moreover, the oxide dislocation interaction in oxide dispersed in iron follow the orowan unpinning mechanism accompanied by loops around oxide. The values of critical unpinning stress for all models were analyzed and compared. Atomic insights on the interaction mechanism indicate that the interaction mechanism is essentially the same for void and a P cluster in Fe i.e. orowan unpinning mechanism. The presence of oxide in Fe matrix during its interaction follows the orowan unpinning mechanism along with a dislocation loop around the oxide and its area is proportional to the size of the oxide. The critical unpinning stress was compared and analyzed for each model. This work will provide a unique and valuable insight into the strengthening mechanism due to dispersed oxides by providing new parameters for the multi-scale simulation. Our results demonstrate that oxide impedes dislocations and offers hindrance for edge dislocations to saturate further. Furthermore, our simulation results provide atomic insight into the onset of plasticity in iron alloys.