An atomistic-to-microscale computational analysis of the dislocation pileup-induced local stresses near an interface in plastically deformed two-phase materials

Taking the two-phase material as a model system, here we perform atomistic-to-microscale computa-tional analysis on how the dislocations pileup is formed at a buried interface through two-dimensional concurrent atomistic-continuum simulations. One novelty here is a simultaneous resolution of the mu m-level dislocation slip, the pileup-induced stress complexity, and the atomic-level interface structure evolution all in one single model. Our main findings are: (i) the internal stresses induced by a pileup spans a range up to hundreds of nanometers when tens of dislocations participate the pileup; (ii) the resulting stress concentration decays as a function of the distance, r, away from the pileup tip, but deviates from the Eshelby model-based 1/r(0.5) , where the interface was assumed to be rigid without allowing any local structure reconstruction; and (iii) the stress intensity factor at a pileup tip is linearly proportional to the dislocation density nearby the interface only when a few dislocations are involved in the pileup, but will suddenly upper bend to a very high level when tens of or more dislocations arrive at the interface. The gained knowledge can be used to understand how the local stresses may dictate the plastic flow-induced phase transformations, twinning, or cracking in heterogeneous materials such as polycrystalline steel, Ti-, Mg-, high entropy alloys, fcc/bcc, fcc/hcp, and bcc/hcp composites, containing a high density of interfaces. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, atomistic-to-microscale computational analysis was performed on a two-phase material to investigate the formation of dislocation pileup at a buried interface. The simultaneous resolution of dislocation slip, pileup-induced stress complexity, and atomic-level interface structure evolution was achieved in a single model. The findings reveal that the internal stresses induced by pileup can span a range of hundreds of nanometers, and the resulting stress concentration decays with distance, deviating from the Eshelby model. Moreover, the stress intensity factor at a pileup tip is linearly proportional to the nearby dislocation density only when a few dislocations are involved, but it significantly increases when tens of or more dislocations arrive at the interface.