Twin boundary reversibility characteristics in {\alpha}-Fe

TL;DR

This study uses molecular dynamics simulations to analyze how coherent twin boundaries in { extalpha}-Fe respond to cyclic shear loading, revealing temperature-dependent reversibility and migration behaviors crucial for microstructure stability.

Contribution

It provides new insights into the temperature and size effects on twin boundary reversibility and migration mechanisms in { extalpha}-Fe under cyclic shear.

Findings

Twin boundaries show shear coupled migration and irreversibility at low temperatures.

Reversibility improves significantly at around 1500 K.

Twin boundary migration involves layer-by-layer propagation via partial dislocations.

Abstract

Understanding the grain boundary deformation dynamics is very crucial to designing materials with stable microstructures. With this quest, the deformation behavior of coherent twin boundary under cyclic shear loading has been studied in {\alpha}-Fe using molecular dynamics simulations to understand the influence of strain amplitude and temperature. Twin boundary exhibited shear coupled migration along with cyclic irreversibility character at lower temperatures and gained almost perfect reversibility at higher temperatures of around 1500 K. TB exhibited more sliding than migration with an increase in temperature. The stress associated with the migration of twins was observed to fluctuate around its average value. This was caused by layer by layer propagation of twin boundary through the activity of 1/6 <111> = 1/12 <111> + 1/12 <111> type edge partial dislocations on "\{"112"\}" twin plane. Complete twin reversibility and complex TB migration were noticed in the presence of multiple parallel twin nanowires. Twin migration was observed at the larger size nanowires with a proper combination of boundary conditions and strain rates; otherwise, it was absent. The influence of shear strain amplitude in offsetting the twin boundary was found to be minimal.