Effects of the grain size and shape on the flow stress: A dislocation dynamics study

TL;DR

This study uses dislocation dynamics simulations to analyze how grain size and shape affect flow stress in copper, revealing a linear relationship with the inverse square root of grain size and highlighting the influence of grain orientation and shape.

Contribution

It introduces a detailed simulation approach to quantify the effects of grain size and shape on flow stress, including a new model for grain shape influence.

Findings

Flow stress varies linearly with inverse square root of grain size.

Grain orientation and shape significantly affect flow stress.

A simple model explains the grain shape influence on the size effect.

Abstract

Dislocation dynamics simulation is used to investigate the effect of grain size and grain shape on the flow stress in model copper grains. We consider grains of 1.25-10 $\mu$m size, three orientations (<135>, <100> and <111>) and three shapes (cube, plate and needles). Two types of periodic aggregates with one or four grains are simulated to investigate different dislocation flux at grain boundaries. It is shown that in all cases the flow stress varies linearly with the inverse of the square root of the grain size, with a proportionality factor varying strongly with the grain orientation and shape. Simulation results are discussed in the light of other simulation results and experimental observations. Finally, a simple model is proposed to account for the grain shape influence on the grain size effect.