Atomistic simulation study of tensile deformation in nanocrystalline and single-crystal Au

摘要

The effect of notch size (r) on nanocrystalline (NC) and single-crystal (SC) Au at a temperature of 300 K under tension testing is studied using molecular dynamics simulations based on the many-body embedded-atom potential. The effect is investigated in terms of atomic trajectories, common neighbor analysis, and the stress-strain curve. The simulation results show that for the NC samples, stacking faults nucleate at grain boundaries (GBs), propagate inside grains, and eventually are terminated by GBs or transect them. For tensile-deformed NC and SC samples with larger r values, necking and breaking occur faster, which indicates that ductility decreases. SC samples exhibit larger yield strength and ultimate strength than those of NC samples. SC samples have a longer elastic deformation period due to their lack of GBs. For NC samples, increasing the r value increases Young's modulus but decreases the yield point; in addition, it decreases mechanical strength and speeds up the formation of necking.