Deformation of Nanocrystalline Metals under Nanoscale Contact

摘要

Quasicontinuum simulations have been performed to study the nanoindentation of a columnar grain boundary (GB) network in nanocrystalline Al at zero temperature. The objective was to investigate the relationship between structural evolution at GBs and incipient plasticity when the average grain size becomes smaller than the nanoindenter tip radius. A GB network made of low-angle and high-angle < 110 > tilt GBs was simulated by generating randomly-oriented 5-nm grains at the surface of a 200 nm-thick film. The major conclusions of this investigation are that (1) nanocrystalline GB networks cause significant softening effects at the contact interface; (2) GB movement and deformation twins are found to be the predominant deformation modes in columnar nanocrystalline Al; and (3) the cooperative grain deformation behavior is driven by the redistribution of atomic shear stress gradients between grains.