Activation volume and deviation from Cottrell–Stokes law at small grain size

Dependence of activation volume with flow stress is examined for metals with grain size lower than 0.3μm and larger than few tens of nanometers, where plastic deformation is most likely to be governed by a combination of grain boundary sliding and dislocations activity. The experimentally observed deviation from the classic linear behavior given by Cottrell–Stokes law [Basinski, Z.S., 1974. Forest hardening in face centered cubic metals. …