Summary: Dislocation Confinement and Ultimate Strength in Nanoscale Polycrystals
, Peter M. Anderson1
, Michael Mills1
, and Peter Hazzledine2
Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, U.S.A.
Universal Energy Systems Inc., Dayton, OH 45432 USA
Nanoscale polycrystalline metals typically exhibit increasing hardness with decreasing grain
size down to a critical value on the order of 5 to 30 nm. Below this, a plateau or decrease is
often observed. Similar observations are made for nanoscale multilayer thin films. There, TEM
observations and modeling suggest that the hardness peak may be associated with the inability of
interfaces to contain dislocations within individual nanoscale layers. This manuscript pursues
the same concept for nanoscale polycrystalline metals via an analytic study of dislocation
nucleation and motion within a regular 2D hexagonal array of grains. The model predicts a
hardness peak and loss of dislocation confinement in the 5 to 30 nm grain size regime, but only if
the nature of dislocation interaction with grain boundaries changes in the nanoscale regime.