In situ synchrotron research of phase formation in mechanically activated 3Ti + Al powder composition during high-temperature synthesis under the condition of heating with high-frequency electromagnetic fields

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%.

In situphase formation during high-temperature synthesis in clad mechanocomposites based on the Ti–Al system

“…For a detailed study of in situ phase formation in the synthesis of clad precursors of Ti 64 wt% + Al composition, synchrotron radiation time-resolved diffractometry was applied. It should be noted that similar studies were previously conducted for mechanoactivated samples of the same composition, but without the deposited shell on them; the results are given by Loginova et al (2019a).…”

“…Mechanoactivation pretreatment has also been found to lower the maximum synthesis temperatures by reducing the reaction activation energy (Adeli et al, 2017;Xu et al, 2006). Loginova et al (2019a) considered in detail the phase transformations for mechanoactivated Ti +Al mixture. It was found that the characteristic heating rate is 500 K min À1 , and the ignition temperature is lower than the melting of the fusible component (about T = 555 C).…”

“…In this work, the Ti-Al system, which has wide application in the technologies of modern materials science, is investigated using model experiments (Sina & Iyengar, 2015;Chin & Biederman, 1992;Okamoto, 1993;Lee et al, 2000). Loginova et al (2019a) studied in detail the effect of preliminary mechanical activation of a Ti + Al powder mixture on the processes of high-temperature synthesis. In this regard, it is of particular interest to conduct model experiments to study the effect of Ti + Al mechanocomposites cladding on phase formation and thermal synthesis processes.…”

Surfacing of Ti-Al System Mechanocomposites by Magnetron Deposition

“…5. We assume that surfacing of mechanocomposites will provide additional possibilities for controlling the reaction of high-temperature synthesis in thermal explosion mode [18][19][20][21][22][23][24]…”

Features of High-Temperature Synthesis in Clad Mechanocomposites of Ti-Al System

“…Centripetal mill acceleration 40 g, activation time 7 min. The choice of mechanical activation modes was determined from previous studies [12,13].…”