  Amorphous/crystalline multilayer structures of Fe-P alloys were deposited
electrochemically using the single bath technique. Hall-Petch behavior of
microhardness with respect to sublayer thickness was observed down to a
sublayer thickness of 15 nm. For thinner sublayers, a hardness plateau was
obtained. The transition at a sublayer thickness of 15 nm coincides with the
loss of the multilayer structure as observed in transmission electron
microscopy. The transition is a possible result of a change in the amorphous to
crystalline sublayer thickness ratio and the interface roughness development
during the deposition process. Additionally, crack deflection at the interfaces
was observed for the layered structures with small sublayer thickness in
microbending experiments.
