On the kinetics of phase and structural transformations upon mechanical alloying

Based on the data of X-ray diffraction analysis and Mössbauer spectroscopy, a comparative analysis of kinetic dependences of the processes of structure and phase formation upon mechanoactivation of model systems with different types of interaction has been conducted. As model systems, we used systems with both negative (Fe-Mn, Fe-Co, Fe-Ni) and positive (Fe-Cu) deviations of the heats of mixing of the components from ideality. Two main types of the kinetic dependence of the evolution of the phase composition upon mechanical alloying have been considered: a simple linear dependence (found for the Fe70Ni30 and Fe65Co35 compositions) and a two-stage one (found for Fe10Co90, Fe50Mn50, and Fe86.5Cu13.5). It has been established that a scheme considering mechanical alloying of metallic materials as a result of the action of two processes (deformation and relaxation of interphase boundaries) makes it possible to substantiate the experimentally observed sequence of phase transformations on the basis of the thermodynamic driving forces of the process. The model concepts developed adequately describe the results of experimental investigations and, in particular, allow one to qualitatively account for the two-stage character of dependences of the phase composition on the mechanoactivation time.