Structural state of the Ti–Al powder mixture at various stages of mechanoactivation treatment

Mechanocomposites used as precursors in high-temperature synthesis increase the possibility of chemical reactions executed in a solid-phase mode: they expand the concentration limits of combustion, change burning temperature and rate, ignition temperature, etc. Issues related to the possibility of changing the mechanocomposite structure at both macro and micro levels canbe important for subsequent obtaining of a synthesis product with a required composition, structure and properties. This paper provides selection of optimal modes for preliminary mechanical activation to obtain precursors for high-temperature synthesis. The main controlling parameters of the activation action on the Ti + Al powder mixture were mechanical activation time and power load intensity. One of the determining factors for choosing the optimal mode of mechanical activation is the formation of maximum possible microstrains without the appearance of mechanical synthesis products at the given grinding parameters. It follows from the analysis of structural parameters that these conditions can be achieved at the mill energy intensity of 20 g within over 13 min of mechanical activation impact, but it is not possible to implement due to powder mixture sticking to grinding media. 7-minute treatment at the intensity of 60 g leads to the beginning of mechanochemical synthesis, which limits the mechanical activation time interval. Thus, it is necessary to select activation modes corresponding to the mechanical activation time of 7 minutes at the ball mill energy intensity of 40 g to ensure subsequent implementation of high-temperature synthesis. The studied morphology of mechanocomposites obtained in this mode demonstrated that a plastic aluminum matrix creates conditions for an ideal contact of reagents, and the material formed can be regarded as an elementary reactor in the volume of which the most favorable conditions for solid-phase diffusion are created.

powder mixture, aluminum, titanium, mechanical activation treatment, structural parameters, microstrains, microstructure, mechanocomposites

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