The driving force governing room temperature grain coarsening in thin gold films

TL;DR

This paper investigates the mechanism behind room-temperature grain coarsening in gold films under cyclic strain, revealing an isotropic process driven by yield stress differences rather than shear-coupled migration.

Contribution

It introduces a thermodynamic model based on yield stress differences to explain grain coarsening, challenging existing shear-coupled migration theories.

Findings

Grain coarsening is isotropic and not orientation-dependent.

Yield stress differences drive the coarsening process.

Shear-coupled migration model does not explain the observations.

Abstract

Strong room-temperature grain coarsening in gold films on polyimide induced by cyclic uniaxial mechanical strain is demonstrated. Detailed electron backscatter diffraction analysis revealed that, in contrast to the predictions of shear-coupled grain boundary migration model, the grain coarsening is isotropic and coarsened grains do not exhibit any specific crystallographic orientations or misorientations to the neighboring grains. It is shown that a thermodynamic model where the driving force appears due to the difference in yield stresses between the grains with different sizes provides an adequate explanation of the experimental data.