[SY-C3] Symposium C-3

[SY-C3] Investigation of the Hall-Petch Effect with DD Simulation

^○Maoyuan Jiang^1,2, Benoit Devincre², Ghiath Monnet¹ (1.EDF - R&D, Les Renardieres, France, 2.Laboratoire d'Etude des Microstructures, CNRS/ONERA, France)

Dislocation Dynamics (DD) simulation is used to identify the elementary mechanisms controlling the Hall-Petch (HP) effect on the dislocation scale. The influence of grain size is explored by considering simple periodic polycrystalline aggregates made of grains with cube, plate or needle shapes. We show that the HP effect is globally well reproduced with DD simulations. The HP constant is found to be a function of the grain orientations and shapes. A model is proposed to quantify the influence of the grain morphology. The simulated HP effect is justified by the existence of a backstress inside the grains that emerges from strain incompatibility between grains in a deformed polycrystal. As theoretically expected, Geometrically Necessary Dislocations (GND) are found to accumulate at grain boundaries to accommodate the distortion field discontinuities. By virtue of the Nye’s tensor, the above property can be directly tested and quantified in DD simulations. For the simplest simulation geometry, the calculated backstress is compared with theoretical predictions. Those results suggest a new strategy for the prediction of the grain size effect in crystal plasticity models.