A Predictive Strength Model for Cu/Ni Nanolayered Composites with FCC Interfacial Layers Under Loading Parallel to the Interface

Abstract

Nanolayered metallic composites exhibit ultra-high strength but suffer from inadequate ductility. Constructing interfacial layers becomes an effective strategy to enhance their strength and ductility. However, extensive experimental studies have focused on the strengthening and toughening mechanism of some special interfacial layers under loading normal to the interface, a systematic understanding of how interfacial layer characteristics influence the mechanical response remains unclear, especially under loading parallel to the interfaces. Here, molecular dynamics simulations using the LAMMPS code with embedded atom method potentials are performed to investigate the tensile deformation of Cu/Ni nanolayered composites with various interfacial layers made by six different FCC metals, i.e., Ag, Al, Au, Pb, Pd, and Pt, under loading parallel to the interfaces. Our simulation results reveal that the strength of composites is governed by the metallic element of interfacial layers. The composites with Pd and Pt interfacial layers exhibit the highest and lowest strength, respectively, showing a maximum strength difference of 1.09 GPa. The strength variation is attributed to the synergistic interplay of multiple characteristics of interfacial layers, rather than from a single dominant factor. Furthermore, a quantitative mapping relationship between the strength of composites and the characteristic parameters of the interfacial layers was established on the basis of the Voigt model and the dislocation nucleation behavior. Accordingly, the strength can be expressed as a function of three decisive determinants: the strain energy density required for dislocation nucleation in the pure metal corresponding to the interfacial layers, the elastic modulus of that pure metal, and a parameter related to the stress concentration level at the interfaces. A higher value of the former two factors, combined with a lower value of the latter, corresponds to a higher strength.