Inverse Hall-Petch Behavior in Nanocrystalline Aluminum Using Molecular Dynamics

Abstract

This work investigates the mechanical behavior of nanocrystalline aluminum, with special focus on deformation mechanisms, using molecular dynamics simulations with an interatomic potential parameterized by the authors. To this end, four nanocrystalline samples with grain sizes ranging from 8,2 to 14,2 nm were constructed, each with a volume of 15 x 15 x 20 nm3. As expected, the data from the tensile tests at a strain rate of 1,0 x 109 s−1 showed an inverse Hall-Petch relationship. The work hardening behavior revealed no significant gain in mechanical strength. The dislocation analysis indicated that perfect dislocation density decreases during tensile testing, while the Shockley partials increase. Grain boundary-mediated plasticity was evidenced with atomic diffusion along grain boundaries, as well as by grain rotation. Thus, it is concluded that the conventional plastic deformation mechanisms of metals are not preponderant for nanocrystalline aluminum.