Nanostructured NiFe film was obtained on silicon with a thin gold sublayer via pulsed
electrodeposition and annealed at a temperature from 100 to 400 ◦C in order to study the effect of
heat treatment on the surface microstructure and mechanical properties. High-resolution atomic
force microscopy made it possible to trace stepwise evolving microstructure under the influence
of heat treatment. It was found that NiFe film grains undergo coalescence twice—at ~100 and
~300 ◦C—in the process of a gradual increase in grain size. The mechanical properties of the Au/NiFe
nanostructured system have been investigated by nanoindentation at two various indentation depths,
10 and 50 nm. The results showed the opposite effect of heat treatment on the mechanical properties
in the near-surface layer and in the material volume. Surface homogenization in combination with
oxidation activation leads to abnormal strengthening and hardening-up of the near-surface layer.
At the same time, a nonlinear decrease in hardness and Young’s modulus with increasing temperature
of heat treatment characterizes the internal volume of nanostructured NiFe. An explanation of this
phenomenon was found in the complex effect of changing the ratio of grain volume/grain boundaries and increasing the concentration of thermally activated diffuse gold atoms from the sublayer to the
NiFe film.
