PHASE-TRANSFORMATIONS INDUCED BY MECHANICAL ALLOYING IN BINARY-SYSTEMS

Recent progress in the understanding of metastable and equilibrium phase formation induced by mechanical alloying (MA) of elemental powders is reviewed, with an emphasis on our recent results obtained using a combined experimental and modeling approach. Both the kinetic and thermodynamic aspects are examined. It is shown that alloy phase transformation can proceed under different constraints and via different mechanisms. In addition to the mechanism of a layer diffusion under metastable equilibrium, MA can be controlled by polymorphous constraints, or occur by self-sustained, exothermic reactions. It is demonstrated that, with properly determined thermodynamic functions of metastable phases, thermodynamics can be used to describe phase transformation by MA in limiting cases. The determination of thermodynamic functions of metastable phases is illustrated with several examples.