A nucleation theory for yielding of nearly defect-free crystals: understanding rate dependent yield points

TL;DR

This paper introduces a nucleation-based theory for the yield point in defect-free crystals, explaining experimental data over fifteen orders of magnitude without relying on power law assumptions.

Contribution

It proposes a new nucleation theory for crystal yielding that accounts for rate dependence without using power law models, unifying diverse experimental observations.

Findings

The theory explains yield points over fifteen orders of magnitude in time.

It accounts for the weak rate dependence observed in experiments.

The relation derived is not a power law, contrasting previous models.

Abstract

Experiments and simulations show that when an initially defect free rigid crystal is subjected to deformation at a constant rate, irreversible plastic flow commences at the so-called {\em yield point}. The yield point is a weak function of the deformation rate, which is usually expressed as a power law with an extremely small non-universal exponent. We re-analyze a representative set of published data on nanometer sized, mostly defect free, Cu, Ni and Au crystals in the light of a recently proposed theory of yielding based on nucleation of stable stress-free regions inside the metastable rigid solid. The single relation derived here, which is {\em not} a power law, explains data covering {\em fifteen} orders of magnitude in time scales.