The formation of nanocrystalline and amorphous phases and unstable and stable solid solutions by mechanical alloying is analyzed by considering the mixture of the interfacial components of the elements as an ideal solution. We used the Gibbs free energy and equilibrium volume equations together with the results obtained for the excess Gibbs free energy for the metals, in nanometric form, to calculate activation energies associated with diffusive processes responsible for grain growth, grain boundary migration, atomic migration, and nucleation of new phases. Results obtained from this thermodynamic approximation seem to be confirmed experimentally by the formation of nanocrystalline ${\mathrm{Fe}}_{67}{\mathrm{Ge}}_{33}$ and amorphous ${\mathrm{Co}}_{67}{\mathrm{Ge}}_{33}$ alloys by mechanical alloying in our laboratory.

• Received 4 January 2000

DOI:https://doi.org/10.1103/PhysRevB.62.8871