Twinning induced by elastic anisotropy in FCC crystals

TL;DR

This paper develops a model based on elastic anisotropy theory to predict the critical resolved shear stress for twinning in FCC crystals, validated against experimental data and revealing how shear stress influences twinning nucleation.

Contribution

It introduces a novel approach combining elastic anisotropy and energy considerations to predict twinning CRSS in FCC crystals, accounting for temperature and strain rate effects.

Findings

Predicted CRSS aligns with experimental results.

Shear stress along <112> reduces interface energy.

Twinning nucleation can be promoted by specific shear directions.

Abstract

Dislocation slip and deformation twin are widely regarded as two important mechanisms of active competition in the process of plastic deformation. Calculating and comparing the critical resolved shear stress (CRSS) of two deformation modes are the key to discussing the mechanical properties reflected by different mechanisms in crystals. Here, the paper proposes a model to predict the CRSS of discrete twins, resembling thin layers, using the elastic anisotropy theory and a macroscopic energy perspective. In addition, the directionality of deformation twinning is also verified. We investigated twinning in FCC crystals to illustrate the methodology, and predicted the CRSS of twinning under different variables such as temperature and strain rate, both of which were in excellent agreement with experimental and other theory results. It draws the conclusion that we can promote twinning nucleation by applying shear stress along the <112> direction to reduce the interface energy as a resistance term and increase the difference in strain energy for twinning nucleation. This conclusion provides a guiding direction for exploring and accurately predicting the conditions of twinning in FCC crystals in future.