Deformation mechanism transitions in nanoscale fcc metals

We consider possible mechanisms that lead to transitions in the mechanisms of deformation in fcc metals and alloys. In particular, we propose that, when grain sizes are below a critical size (i.e. below 100 nm), deformation can occur via the emission of stacking faults from grain boundaries into the intragranular space. A model is developed that accounts for observed experimental data and which, in turn, shows how stacking-fault energy together with shear modulus determines achievable strength. A mechanism is proposed based on this model for transitions at both high and quasistatic strain rates, including grain-boundary sliding.