No abstract

An in situ synchrotron study of the specific features of the phase formation dynamics in mechanically activated 16 wt% Al + Ti powder composition is described, the high-temperature synthesis being carried out under the condition of high volume inflammation by means of inductive heating. The kinetics of the phase formation were registered with an experimental complex, especially designed, constructed and adjusted for the method of dynamic diffraction analysis in synchrotron radiation beams. It has been experimentally in situ shown that increasing the time of mechanical activation of the initial powder mixture reduces the temperature at which components start to react and the time of realization of the high-temperature synthesis. With the latter set at 1 min of mechanical activation, the temperature of the reaction in the mixture is T = 603°C; at 3 min of mechanical activation, T = 442°C; and at 7 min, T = 359°C. The maximum burning temperatures are: for 1 min of mechanical activation, T max = 1080°C; for 3 min, T max = 1003°C; and for 7 min, T max = 820°C. It was found that formation of both stable compounds Ti3Al, TiAl3, TiAl2, TiAl and metastable phases Ti9Al23, Ti5Al11, Ti2Al5, Ti3Al5 occurs at the stage of primary structure formation, before the system goes to thermal explosion. High-temperature synthesis of a mixture of the studied composition takes place without formation of a liquid phase, in the solid-phase combustion mode. It was found that the increase in the time of mechanical activation of the initial powder mixture contributes to the formation of a product with a dominant content of intermetallic compound Ti3Al. By synthesis of the powder mixture of composition 16 wt% Al + Ti, mechanically activated for 7 min, the content of Ti3Al in the final product was found to be 68%.

No abstract

No abstract

In situ synchrotron studies of structure and phase formation dynamics in mechanically activated (t = 7 min, power density 40 g) and mechanically activated with subsequent irradiation by γ‐quanta 60Co powder mixture (Ti 64 wt% + Al) during high‐temperature synthesis by the method of thermal explosion using induction heating are described. In situ high‐temperature synthesis was carried out on the created experimental complex adapted for synchrotron X‐ray diffraction methods. The sequence of formation and time–temperature interval of the metastable and main phases were determined. The impact of preliminary mechanical activation and of γ‐irradiation on the macrokinetic parameters of the synthesis were studied experimentally in situ. It has been established that the impact of γ‐irradiation on the mechanically activated powder mixture of the composition Ti 64 wt% + Al leads to a change in the thermal parameters of combustion: the maximum synthesis temperature and the burning rate decrease. The heating rate for the non‐irradiated mixture is 204.8 K s−1 and that for the irradiated mixture is 81.6 K s−1. The dependences of mass fractions of the synthesized compounds on time and temperature were calculated from the stage of preheating until completion of the thermal explosion. A single‐phase equilibrium product of the composition γ‐(TiAl) is formed in γ‐irradiated mechanically activated mixture when the system reaches maximum temperature. The synthesized product of the mechanically activated mixture without γ‐irradiation contains 72% γ‐(TiAl); TiAl3 (26%) and residual Ti (2%) are also observed.