Dynamics of structure formation processes in mechanically activated powder mixture TI+AL under conditions of continuous heating. High temperature stage

Abstract

Аbstract With the use of time-resolved X-Ray diffraction, the analysis of the phase formation dynamics processes in mechanically activated powder mixture of Ti + Al composition in the thermal explosion mode was carried out. The synthesis was conducted under conditions of heating by an external source of constant power. It was found that at the stage of low-temperature heating (preheating stage), a significant amount of reaction products (intermetallic phases) is formed. A possible reason for this is the presence of disordered transition zones that form at the interface between the reactants in the process of preliminary mechanical activation. However, in the process of nonequilibrium synthesis (thermal explosion), the formation of the only compound γ -TiAl occurs. It was established that the structural changes continue after completion of the chemical reaction. At the first stage of high-temperature annealing, the processes of structural relaxation (which are not accompanied by the appearance of new compounds) are realized. At the second stage, the processes of transition to a thermodynamically equilibrium state occur. It was shown that the forced cooling of the system at various stages of the synthesis can be a way of controlling the structure, composition and, as a consequence, properties of the synthesis product.