Glide dislocation nucleation from dislocation nodes at semi-coherent {1 1 1} Cu–Ni interfaces

Abstract

a b s t r a c tUsing atomistic simulations and dislocation theory on a model system of semi-coherent {1 1 1} interfaces, it is shown that misfit dislocation nodes adopt multiple atomic arrangements corresponding to the creation and redistribution of excess volume at the nodes. Four distinctive node structures were identified: volume-smeared nodes with (i) spiral or (ii) straight dislocation patterns, and volume-condensed nodes with (iii) triangular or (iv) hexagonal dislocation patterns. Volume-smeared nodes contain interfacial dislocations lying in the Cu-Ni interface but volume-condensed nodes contain two sets of interfacial dislocations in the two adjacent interfaces and jogs across the atomic layer between the two adjacent interfaces. Under biaxial tension/compression applied parallel to the interface, it is shown that the nucleation of lattice dislocations is preferred at the nodes and is correlated with the reduction of excess volume at the nodes.

Shock-induced plasticity in semi-coherent {111} Cu-Ni multilayers

“…Much recent MD simulation-based research has addressed the strengthening eff ects of interfaces and the underlying micromechanisms (Shao and Medyanik (2010); Shao et al (2015); Mitchell (2002); Rao and Hazzledine (2000); Wang et al (2008b,a); Ghosh and Arroyo (2013); Peng and Wei (2016); Zhu et al (2015); Salehinia et al (2014); Li et al (2012b); Zbib et al (2011);). However, studies using MD simulations to understand the atomic-scale details of interactions between shockwaves and interfaces have been infrequent.…”

“…As a special class of metallic multilayer materials, the mechanical behaviors of Cu-Ni multilayers have attracted significant recent interest (Misra et al (1998); ; Liu et al (2011a); Rao and Hazzledine (2000); Mitchell (2002); Yan et al (2013); Liu et al (2012); Yahalom et al (1989)). Shao et al (2013Shao et al ( , 2014Shao et al ( , 2015 recently reported observations from MD simulations of misfit dislocation structures in Cu(111)/Ni(111) semi-coherent interfaces. They found that the interfaces contained several structures, including normal FCC stacking structures, intrinsic stacking-fault structures, misfit dislocations, and misfit dislocation intersections (nodes).…”

“…They found that the interfaces contained several structures, including normal FCC stacking structures, intrinsic stacking-fault structures, misfit dislocations, and misfit dislocation intersections (nodes). The mechanical behaviors of these semi-coherent interfaces under biaxial tension and compression applied parallel to the interfaces were studied by Shao et al (2015). The nucleation of lattice dislocations occurred preferentially at the nodes, correlated with reduction of excess volume at these points.…”

Relaxation Mechanisms, Structure and Properties of Semi-Coherent Interfaces

“…The triangular nodes can transform into an expanded hexagonal structure (Figure 4d) when it is relaxed at a finite temperature of above 10 K. This structure has been observed in the experiment. This structure, referred to as the volume-condensed node with hexagonal dislocation pattern, is formed from the triangular nodes after a series of complex dislocation reactions (detailed information in [46]). The dislocation structure of the node also involves two adjacent (111) planes (Ni1-Cu1 and Cu1-Cu2).…”

Cooperative dissociations of misfit dislocations at bimetal interfaces

“…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. Such core spreading significantly reduces stress/strain concentrations at the interface and thus traps the dislocations there, strengthening the material by creating a high activation barrier for dislocation nucleation.…”