The introduction of twin boundaries within nanocrystalline grains has given scientists an opportunity to enhance mechanical properties that were usually mutually exclusive: strength and ductility. This research was focused on developing a complete understanding of the influences of twin width, grain size and temperature on the deformation characteristics and properties of nanotwinned Cu by large-scale molecular dynamics simulations. Simulation results have shown that a material's toughness could be enhanced by introducing nanotwins, and the enhancement was more pronounced for the higher twin density structures and at lower temperatures. Nanotwinned grains were found to be highly anisotropic in their plastic response; ductile along twin boundaries but strong across them. A random polycrystalline sample gains toughness through the combined response of variously oriented grains. At extremely low temperature, toughness values were elevated further due to depressed dislocation activities inside the grains. The study has also revealed that, unlike twin width refinement, grain size refinement may not always yield superior properties, and may deteriorate material toughness.

A Molecular Dynamics Study of Twin Width, Grain Size and Temperature Effects on the Toughness of 2D-Columnar Nanotwinned Copper. I.Shabib, R.E.Miller: Modelling and Simulation in Materials Science and Engineering, 2009, 17[5], 055009