Deformation in amorphous-crystalline nanolaminates -- an effective-temperature theory and interaction between defects

TL;DR

This paper develops a micromechanics model using an effective-temperature framework to describe defect interactions at the amorphous-crystalline interface in nanolaminates, explaining defect transmission and interface behavior.

Contribution

It introduces a unified effective-temperature model for defect interactions in amorphous-crystalline nanolaminates, linking thermodynamics with defect dynamics at interfaces.

Findings

The ACI acts as a sink for dislocations.

The ACI serves as a source of shear transformation zones.

Model shows good agreement with experimental data.

Abstract

Experiments and atomic-scale simulations suggest that the transmission of plasticity carriers in deforming amorphous-crystalline nanolaminates is mediated by the biphase interface between the amorphous and crystalline layers. In this paper, we present a micromechanics model for these biphase nanolaminates that describes defect interactions through the amorphous-crystalline interface (ACI). The model is based on an effective-temperature framework to achieve a unified description of the slow, configurational atomic rearrangements in both phases when driven out of equilibrium. We show how the second law of thermodynamics constrains the density of defects and the rate of configurational rearrangements, and apply this framework to dislocations in crystalline solids and shear transformation zones (STZs) in amorphous materials. The effective-temperature formulation enables us to interpret the observed movement of dislocations to the ACI and the production of STZs at the interface as a "diffusion" of configurational disorder across the material. We demonstrate favorable agreement with experimental findings reported in (Kim et al., Adv. Funct. Mater., 2011), and demonstrate how the ACI acts as a sink of dislocations and a source of STZs.