Tensile Deformation of Ni/Ti Multilayers: Coupled Effects of Modulation Period and Strain Rate from Molecular Dynamics Simulations

Abstract

The mechanical response of Ni/Ti multilayers is governed by the interplay between interface-mediated deformation and structural transformations in the constituent layers. Here, molecular dynamics simulations are used to investigate the tensile deformation of planar Ni/Ti multilayers with modulation periods of 28.6 nm – 9.5 nm over strain rates of 108 s-1 – 1010 s-1. Decreasing the modulation period reduces the tensile strength by ~8% and substantially modifies the post-yield deformation, including the partitioning of dislocation activity between the Ni and Ti layers and the formation and persistence of deformation-induced BCC Ti. Increasing the strain rate has a comparatively weak effect on tensile strength but systematically delays the structural transformations. Pronounced stacking faults in Ni develop at ~8% strain at 108 s-1 but only at ~13% at 1010 s-1. At the highest strain rate, the HCP-to-BCC transformation in Ti is also delayed and becomes more abrupt, producing finer and more dispersed BCC regions. Overall, the results show that the modulation period primarily determines the deformation pathway and distribution of plasticity between the constituent layers, whereas the strain rate primarily controls the onset and kinetics of the deformation processes.