Interfacial properties of Cu-Nb multilayers as a function of dislocation/disconnection content

N Abdolrahim and IN Mastorakos and HM Zbib and DF Bahr, TMS2011 SUPPLEMENTAL PROCEEDINGS, VOL 2: MATERIALS FABRICATION, PROPERTIES, CHARACTERIZATION, AND MODELING, 75-82 (2011).

Cu-Nb nanoscale metallic multilayers (NMM) exhibit very high strength when their thickness becomes less than 50nm. Incoherent or opaque interfaces play a very significant role in defining the overall behavior of the NMM structures. Due to discontinuity of slip systems, interfaces shear easily and act as barriers for slip transmission between layers; meaning that these interfaces have relatively low shear strengths and high potential in attracting glide dislocations within the layers. The interface properties evolve continuously during deformation by absorbing dislocations, leaving disconnections at the interface. These disconnections, which basically can be defined as the composition of a dislocation within the interface and a step, also act as barriers for slip transmission. The effect of such disconnections on the strengthening mechanisms of nanolayers is explored using MD simulations. The interfacial strain energy is computed for a various dislocation configurations. In particular energy maps are developed for a sheared interface as a function of dislocation content and disconnection density. Such measurements can be used in the development of a hardening law for NMM with incoherent interfaces.

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