Indentation-induced plastic behavior of nanotwinned CuNi alloy: an atomic simulation

Abstract

This study uses molecular dynamics simulations to explore the mechanical properties of a nano-twinned copper-nickel alloy through nano-indentations. The effects from twin boundary angle and spacing on the alloy’s behavior are mainly focused on. It is found that the plastic deformation process is primarily driven by dislocation generations, slips, and interactions between dislocations and twin boundaries, all combined affecting the alloy’s hardness. Significant findings include: (1) hardness initially decreases and then increases with twin boundary angle increasing; when the twin boundary spacing is greater than 1.25 nm, hardness can be predicted by using a simple proposed model; (2) dislocation density experiences significant variations, leveling off at an indentation depth around 1.0 nm; (3) when twin boundary spacing exceeds 1.25 nm, plastic deformation is dominated by dislocation nucleation, slips, and interactions with twin boundaries, while smaller spacings lead to twin boundary migration and the presence of independent dislocation loops, giving rise to force fluctuations along indentation process.