Abstract
This work highlights new results on the synthesis of the TiAl3 intermetallic phase using self-propagating high-temperature synthesis. This method is considered a promising sintering route for intermetallic compounds. It was found that the reactions proceed in two stages. Below the melting point of aluminum, the Ti2Al5 phase forms at 450 °C after long annealing times by a direct solid-state reaction between the aluminum and titanium, and is converted consequently to TiAl3. This is a completely new finding; until now, many authors have believed in the preferential formation of the TiAl3 phase. The second stage, the self-propagating strongly exothermic reaction, proceeds above the melting point of aluminum. It leads to the formation of the TiAl3 phase accompanied by Ti2Al5 and Ti3Al phases. The reaction mechanism was shown in the form of chemical equations, which were supported by calculating Gibbs energy. Reaction temperatures (Tonset, Tmaximum, and Toffset) were determined after induction heating thanks to recording by an optical pyrometer. This finding provides completely new opportunities for the determination of activation energy at heating rates, in which common calorimeters are not able to detect a response or even measure. Now, the whole procedure will become accessible.
Highlights
Titanium aluminides belong to a group of modern materials that could replace nickel-based alloys in high-temperature applications such as in the aerospace industry
Cold-pressed powders were heated by various heating rates from the slowest to the fastest one, which can be achieved by induction heating (19–102 ◦ C/min)
All temperatures comprising the start of reaction (Tonset )
Summary
Titanium aluminides belong to a group of modern materials that could replace nickel-based alloys in high-temperature applications such as in the aerospace industry. They offer low density, good high-temperature creep strength, stiffness, high melting points, and oxidation resistance [1,2]. Their wider applications are hampered by low-temperature ductility [1]. Titanium-rich phases (Ti3 Al and TiAl) exist over a large range of compositions, the
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