Abstract
AbstractSequential 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 on Σ3 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.
Highlights
The strength of polycrystalline face-centered cubic (FCC) metals varies characteristically with the average grain size.[1]
The differences between experimental and computational studies are analysed. These two FCC systems are selected based on the works of Chassagne et al.[9] and Jin et al.[12,13] as they have significantly different stable/unstable stacking/twin fault energies that affect the slip transfer reactions; they have planar dislocation cores,[34] which can be well accommodated along interelement boundaries in concurrent atomistic-continuum (CAC)
While large-scale atomistic simulations are desirable in studying slip transfer across grain boundary (GB), our purpose in this paper is to demonstrate the efficacy of coarse-graining in facilitating parametric studies of dislocation/GB reactions concerning a wide range of dislocations and GBs for the same computational resources
Summary
The strength of polycrystalline face-centered cubic (FCC) metals varies characteristically with the average grain size.[1]. Dewald and Curtin[27] conducted simulations of straight pure screw dislocation segments with a Σ3 CTB for Al using the CADD method, and had elucidated several additional criteria for slip transfer beyond those of the classical LRB criteria;[6] we are interested in exploring whether the findings of that kind of quasi-2D study hold up for cases of larger scale full 3D simulations of sequential dislocation slip transfer reactions, which prevail in in situ TEM experiments.[33] The differences between experimental and computational studies are analysed These two FCC systems are selected based on the works of Chassagne et al.[9] and Jin et al.[12,13] as they have significantly different stable/unstable stacking/twin fault energies that affect the slip transfer reactions; they have planar dislocation cores,[34] which can be well accommodated along interelement boundaries in CAC. It is anticipated that this kind of coarse-grained modelling may assist in formulating constitutive laws and rules in describing slip transfer that may be useful upstream in DDD and CPFEM simulations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
