Effect of Copper Segregation at Low-Angle Grain Boundaries on the Mechanisms of Plastic Relaxation in Nanocrystalline Aluminum: An Atomistic Study

Abstract

The paper studies the mechanisms of plastic relaxation and mechanical response depending on the concentration of Cu atoms at grain boundaries (GBs) in nanocrystalline aluminum with molecular dynamics simulations. A nonmonotonic dependence of the critical resolved shear stress on the Cu content at GBs is shown. This nonmonotonic dependence is related to the change in plastic relaxation mechanisms at GBs. At a low Cu content, GBs slip as dislocation walls, whereas an increase in Cu content involves a dislocation emission from GBs and grain rotation with GB sliding.

Modified Taylor Impact Tests with Profiled Copper Cylinders: Experiment and Optimization of Dislocation Plasticity Model

“…The fraction of atoms with broken bonds can be estimated from below as follows: where is the concentration of atoms and is the sublimation energy. The atomistic mechanism of such energy transformation can consist of the formation of vacancies and defect clusters during the annihilation of dislocations observed in MD studies [ 86 , 87 ]. We do not consider that the observed pore-like structures are real pores formed by vacancies, “sublimated atoms”, or due to the plastic growth of pores under negative pressure, because the calculated stress evolution does not reveal sufficiently high negative pressures in the sample.…”