The Structural and Phase State of the TiAl System Alloyed with Rare-Earth Metals of the Controlled Composition Synthesized by the “Hydride Technology”

Abstract

<jats:p>The structural state and the quantitative phase analysis of the TiAl system, alloyed with rare-earth metals synthesized using hydride technology, were studied in this work. Using the Rietveld method, the content of the major phases in the initial system Ti(50 at.%)–Al(50 at.%), as well as Ti(49 at.%)–Al(49 at.%), with alloying additions Ta, Y and Dy having a high accuracy was determined. The methods of scanning electron microscopy, transmission electron microscope and X-ray spectral microanalysis of the local areas of the structure for studying the distribution of alloying elements were used. The energies of lattices of separate phases were also determined after the full-profile specification. All the lattices of the identified structures (about 30) turned out to be stable. It was established that in the Ti(49 at.%)–Al(49 at.%) systems under study with alloying additions of metals Ta, Y and Dy, there were intermetallides composed of AlTi3, TiAl in the hexagonal, tetragonal and triclinic units. It is known that after microalloying alloys by Y and Dy metals, the mass fraction of TiAl phases increases significantly (&gt;70%).</jats:p>

The Influence of Scandium on the Composition and Structure of the Ti-Al Alloy Obtained by “Hydride Technology”

“…The Rietveld method allows for studying the quantitative content of phases from the integral near-surface regions at the scale level, which includes groups of hundreds and more grains. The results of the X-ray phase analysis of the Ti-Al system obtained by HT showed that basic thermodynamically stable phases included intermetallide compounds of Ti 3 Al, TiAl, TiAl 2 and a solid solution of aluminum in α-Ti of the variable composition ( Figure 2 ) [ 19 ]. The X-ray phase analysis of the samples obtained during alloying with scandium of TiAl-Sc showed that they had a complex multiphase structure [ 38 ].…”

“…The samples 50at.%Ti-50at.%Al (Ti-Al) and 49at.%Ti-49at.%Al-2at.%Sc (Ti-Al-Sc) were synthesized by the “Hydride Technology” [ 19 ] at a ratio of Ti:Al=1:1 system to obtain an intermetallide γ-TiAl phase ( Figure 1 ) [ 33 ]. To obtain samples, titanium (Ti ~96 wt.%; average size—90 nm ± 10 nmAdvanced powder technologies LLC, Tomsk, Russia aluminum powder (loading of active aluminum—81%, particle size—90 ± 10 nm, Advanced powder technologies LLC, Tomsk, Russia) and scandium “SkM-1” (scandium composition ~99.98%, CJSC PRM, Novosibirsk, Russia) were used.…”

“…To obtain titanium-aluminum alloys, there are many technologies: to identify selective laser melting [ 14 ], powder metallurgy [ 15 ], laser sintering/melting of aluminum alloy powders [ 16 ], physical vapor deposition [ 17 ], vacuum arc re-melting [ 1 ] and the electric current activated sintering method [ 18 ]. The technique of obtaining the Ti-Al-Sc system by the “Hydride Technology” (HT) is of interest for research purposes [ 19 ].…”

Casting and Solidification of Light Alloys

“…In work [12], the structural and phase states of the TiAl system alloyed with rare earth metals were studied. Tantalum, yttrium and dysprosium were used as additives.…”