Sequential slip transfer across grain boundaries(GB)has an important role in size-dependent propagation of plastic deformation in polycrystalline metals.For example,the Hall–Petch effect,which states that a smaller a...Sequential slip transfer across grain boundaries(GB)has an important role in size-dependent propagation of plastic deformation in polycrystalline metals.For example,the Hall–Petch effect,which states that a smaller average grain size results in a higher yield stress,can be rationalised in terms of dislocation pile-ups against GBs.In spite of extensive studies in modelling individual phases and grains using atomistic simulations,well-accepted criteria of slip transfer across GBs are still lacking,as well as models of predicting irreversible GB structure evolution.Slip transfer is inherently multiscale since both the atomic structure of the boundary and the long-range fields of the dislocation pile-up come into play.In this work,concurrent atomistic-continuum simulations are performed to study sequential slip transfer of a series of curved dislocations from a given pile-up onΣ3 coherent twin boundary(CTB)in Cu and Al,with dominant leading screw character at the site of interaction.A Frank-Read source is employed to nucleate dislocations continuously.It is found that subject to a shear stress of 1.2 GPa,screw dislocations transfer into the twinned grain in Cu,but glide on the twin boundary plane in Al.Moreover,four dislocation/CTB interaction modes are identified in Al,which are affected by(1)applied shear stress,(2)dislocation line length,and(3)dislocation line curvature.Our results elucidate the discrepancies between atomistic simulations and experimental observations of dislocation-GB reactions and highlight the importance of directly modeling sequential dislocation slip transfer reactions using fully 3D models.展开更多
基金supported by the National Science Foundation as a collaborative effort between Georgia Tech(CMMI-1232878)University of Florida(CMMI-1233113)+1 种基金supported in part by the Department of Energy,Office of Basic Energy Sciences under Award Number DE-SC0006539supported by National Science Foundation grant number ACI-1053575.
文摘Sequential slip transfer across grain boundaries(GB)has an important role in size-dependent propagation of plastic deformation in polycrystalline metals.For example,the Hall–Petch effect,which states that a smaller average grain size results in a higher yield stress,can be rationalised in terms of dislocation pile-ups against GBs.In spite of extensive studies in modelling individual phases and grains using atomistic simulations,well-accepted criteria of slip transfer across GBs are still lacking,as well as models of predicting irreversible GB structure evolution.Slip transfer is inherently multiscale since both the atomic structure of the boundary and the long-range fields of the dislocation pile-up come into play.In this work,concurrent atomistic-continuum simulations are performed to study sequential slip transfer of a series of curved dislocations from a given pile-up onΣ3 coherent twin boundary(CTB)in Cu and Al,with dominant leading screw character at the site of interaction.A Frank-Read source is employed to nucleate dislocations continuously.It is found that subject to a shear stress of 1.2 GPa,screw dislocations transfer into the twinned grain in Cu,but glide on the twin boundary plane in Al.Moreover,four dislocation/CTB interaction modes are identified in Al,which are affected by(1)applied shear stress,(2)dislocation line length,and(3)dislocation line curvature.Our results elucidate the discrepancies between atomistic simulations and experimental observations of dislocation-GB reactions and highlight the importance of directly modeling sequential dislocation slip transfer reactions using fully 3D models.
