Dislocation transmission across the Cu/Ni interface: a hybrid atomistic–continuum study

Abstract

The strengthening mechanisms in bimetallic Cu/Ni thin layers are investigated using a hybrid approach that links the parametric dislocation dynamics method with ab initio calculations. The hybrid approach is an extension of the Peierls-Nabarro (PN) model to bimaterials, where the dislocation spreading over the interface is explicitly accounted for. The model takes into account all three components of atomic displacements of the dislocation and utilizes the entire generalized stacking fault energy surface (GSFS) to capture the essential features of dislocation core structure. Both coherent and incoherent interfaces are considered and the lattice resistance of dislocation motion is estimated through the ab initio-determined GSFS. The effects of the mismatch in the elastic properties, GSFS and lattice parameters on the spreading of the dislocation onto the interface and the transmission across the interface are studied in detail. The hybrid model shows that the dislocation dissociates into partials in both Cu and Ni, and the dislocation core is squeezed near the interface facilitating the spreading process, and leaving an interfacial ledge. The competition of dislocation spreading and transmission depends on the characteristics of the GSFS of the interface. The strength of the bimaterial can be greatly enhanced by the spreading of the glide dislocation, and also increased by the pre-existence of misfit dislocations. In contrast to other available PN models, dislocation core spreading in the two dissimilar materials and on their common interface must be simultaneously considered because of the significant effects on the transmission stress.

Mechanical Properties of Nanostructured Metals

“…Large interface transmission strength arises from abrupt changes in dislocation line energy. Surprisingly, interfaces with weak bonding provide large barriers to transmission because they delocalize dislocation cores and trap the dislocation in a low energy state [305][306][307]. The analysis is limited to straight screw dislocations in isotropic layers but is consistent with atomistic [247] and more recent 2D Green's function modeling [234].…”

Cooperative dissociations of misfit dislocations at bimetal interfaces

“…Clearly, these interface-mediated phenomena are generally associated with the characteristics of various interface misfit dislocations, whose structure and configuration govern the interface-facilitated deformation mechanism. 16 Recently, dislocation-interface interaction mechanisms have been proposed for the dislocation nucleation and transmission for low-energy interfaces, such as the semi-coherent Cu{111}/{111}Ni interfaces 14,17 and Kurdjumov-Sachs (KS) and Nishiyama-Wassermann (NW) Cu{111}/{110}Nb interfaces. 5,6,13,18,19 These interfaces are composed of closely packed planes of two adjacent metals, which allow the cores of misfit dislocations to preferably dissociate within the interface.…”

“…C Interface misfit dislocation patterns and interface-facilitated deformation mechanisms have garnered considerable interest because they are well known to play a critical role in determining the ultimate strength and ductility of nanoscale metallic composites. [1][2][3][4][5][6][7][8] An interface may serve as the source for dislocations, [8][9][10][11][12] carry the plastic flow by interface sliding during shearing, 6,13 provide a barrier for dislocation transmission because of the discontinuity of slip systems across an interface, 5,6,13,14 attract or repel incoming lattice dislocations with respect to the character of interface dislocations, 5,15 trap various point defects by distributing the excess potential energy, etc. Clearly, these interface-mediated phenomena are generally associated with the characteristics of various interface misfit dislocations, whose structure and configuration govern the interface-facilitated deformation mechanism.…”

Multiplane-induced widening of stacking faults in fcc metals

“…The approach is an extension [17][18][19] of the Peierls-Nabarro model to multiplanes, where n full dislocations nucleate on successive ͑111͒ slip planes, the dislocation spreading over all planes is explicitly accounted for, and both edge and screw components of the atomic displacements are treated on an equal footing. This allows for the dislocation dissociation into Shockley partials and utilizes the entire generalized stacking fault surface ͑GSFS͒ to capture the essential features of the core structure.…”

“…This allows for the dislocation dissociation into Shockley partials and utilizes the entire generalized stacking fault surface ͑GSFS͒ to capture the essential features of the core structure. 17,19 Each full dislocation is represented by a set of N dislocations with fractional Burgers vector having both edge and screw components. The net force on each fractional dislocation comprises of the elastic forces from all other fractional dislocations on all slip planes, the lattice restoring force across the glide plane derived from the GSFS, and the externally applied Escaig stress.…”