In situ synchrotron research of phase formation in mechanically activated 3Ti + Al powder composition during...

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%.