The temperature and concentration dependences of the critical resolved
shear stress (CRSS) and of the associated activation volume in binary
solid solutions based on cadmium and magnesium are analysed in terms
of the kink-pair nucleation model of solid-solution hardening (SSH). N
umerical calculations of the activation parameters of plastic deformat
ion show that in alloy crystals containing 0.005 to 15 at% solute, the
dislocation segment involved in the activation process gets unpinned
from several solute atoms simultaneously. A single mechanism of SSH is
therefore operative in dilute as well as in concentrated hexagonal cl
ose-packed alloys. It is also inferred that the CRSS of solute-free ma
gnesium crystal is determined by a slip nucleation process, similar to
the kink-pair nucleation at barriers of aligned solute atoms in the m
agnesium-based alloy crystals.