High pressure shear induced microstructural evolution in nanocrystalline aluminum

The microstructural evolution of 4.5 nm grain-sized nanocrystalline aluminum under high pressure shear loading is investigated using molecular dynamics simulations. A compression of 15 GPa is applied to the system concurrently with a shear deformation rate of 3.21 x 10(9) s(-1). Results show that the microstructural evolution is marked by a transient grain refinement regime followed by a steady grain growth process within 1 ns, coarsening the microstructure from 4.5 nm to 5.8 nm average grain size. The grain growth process is mediated by three independent deformation mechanisms: i) grain rotation; ii) grain boundary sliding; iii) and grain boundary migration. While the first two mechanisms are inherent grain boundary deformation mechanisms, the latter is driven by intense dislocation activity. Data indicates that during the deformation the dislocation density surges from 5 to 15 x 10(11) cm(-2) , highlighting the important role of dislocation dynamics in the evolution of the microstructure. These atomistic insights shed light on the underlying complex incipient deformation processes, which are activated during severe plastic deformation of nanocrystalline materials.

Automated summary

The molecular dynamics simulations reveal that under high pressure shear loading, nanocrystalline aluminum with 4.5 nm grain size experiences a transient grain refinement regime followed by a steady grain growth process, increasing the average grain size from 4.5 nm to 5.8 nm within 1 ns. The grain growth process is mediated by three independent deformation mechanisms: grain rotation, grain boundary sliding, and grain boundary migration.