Early stages of the mechanical alloying of TiC–TiN powder mixtures

The present work focuses on the alloying behavior of TiC–TiN powder mixtures submitted to mechanical processing by ball milling. Accurate X-ray diffraction analyses indicate a progressive modification of the unit cell parameters of the TiC and TiN phases, suggesting the formation of TiC- and TiN-rich solid solutions with an increasingly larger content of solutes. Once the discrete character of the mechanical treatment is taken into due account, the smooth change of the unit cell parameters can be explained by a sequence of mutual dissolution stages related to individual collisions. At each collision, the average chemical composition of small amounts of TiC- and TiN-rich phases changes discontinuously. The discontinuous changes can be tentatively ascribed to local mass transport processes activated by the mechanical deformation of powders at collisions.

► Mechanically processed TiC–TiN powder mixtures form two solid solutions.
► An analytical model was developed to describe the mechanical alloying kinetics.
► The amount of powder alloyed at collision was indirectly estimated.
► A few nanomoles of material participate in the alloying process at each collision.
► The chemical composition of the solid solutions was shown to change discontinuously.