Contribution to study the effect of semi-coherent interfaces on the mechanical behavior of metallic multilayers by MD simulations

Abstract

This thesis investigates the role of BCC/BCC semi-coherentAinterfaces on the mechanical response ofNV/Fe bilayers underNnano-indentation, tension, and compression. Using atomistic simulations, we analyze the effects of layer thickness, indenter position, and crystallographic orientation. Our findings reveal that theAV/Fe interfaceZacts asQa dislocationZbarrier during nano-indentation, enhancing hardness through blocking dislocation propagation. This effect is more pronounced for thinner V layers, aligning with the Hall-Petch model. On the other hand, in Fe/V bilayers, the interface promotes dislocation propagation, allowing the decomposition of lattice dislocations in the substrate and leading to a softening effect consistent with the inverse Hall-Petch effect. These results are also observable in the V-Fe-V and Fe-V-Fe multilayers. Under uniaxial loading, analytical investigations of plastic deformation mechanisms during tension and compression reveal a complex interplay between anti-twinning/ twinning and slipQdeformations in bothA V and AFe layers. Tension strengthens the V/Fe bilayer due to the decomposition of misfit dislocation inside V layer and anti-twinning in Fe. Whereas, Softening is observed during compression as deformation initiates in the softer V layer via phase transition. While misfit dislocations decompose inside Fe, activating slip deformation. This tension/compression asymmetry of the V/Fe bilayer is driven by shear strain evolution at the interface.This study provides fundamental insights into dislocation-interfaceQinteractions, strengthening mechanisms, and deformation anisotropy in nano-scale metallic multilayers.