The Al–B–Nb–Ti system

Witusiewicz, V.T.; Bondar, A. А.; Hecht, U.; Velikanova, Т. Ya.

doi:10.1016/j.jallcom.2008.05.008

Cited by 267 publications

(87 citation statements)

References 55 publications

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“…The white colour particles with slightly varied chemical composition of Ti-(36-40)Al-(12-15)Ta (at.%) were identified recently by Lapin et al [10,11] to be a ternary τ phase with B8 2 type crystal structure (space group P6 3 /mmc, Pearson symbol hP6) and Ni 2 In symmetry [11]. The τ phase is similar to a ternary hexagonal Ti 4 Al 3 Nb phase reported by Witusiewicz et al [13] for Ti-46Al-8Nb (at.%) alloy but is different from a binary σ(Ta 2 Al) phase with tetragonal crystal structure resulting from a ternary Ti-Al-Ta phase diagram proposed by Kubaschewski [14]. The lattice parameters a and c of the τ phase measured by XRD technique were found to increase and aspect ratio c/a decreased with increasing ageing time at 750…”

Section: Effect Of Ageing On Microstructuresupporting

confidence: 56%

Long term microstructural stability of intermetallic Ti-46Al-8Ta alloy during ageing at temperatures of 700-800 °C

Lapin¹,

Pelachová²,

Staneková³

et al. 2010

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The lamellar α2(Ti3Al) + γ(TiAl) microstructure of intermetallic Ti-46Al-8Ta (at.%) alloy is unstable and transforms to α2 + γ + τ type at temperatures ranging from 700 to 800• C during long-term ageing up to 10000 h. TEM observations and selected area diffraction patterns show that the ternary τ phase with B82 type structure (space group P63/mmc) is preferentially formed along the grain and lamellar colony boundaries. Volume fractions of the τ and γ phases increase with increasing ageing time at the expense of decreasing volume fraction of the α2 phase at all ageing temperatures. The lattice parameters of the α2 and γ phases change during ageing when compared with those of the as-received alloy. The ageing temperatures have no measurable effect on the lattice parameters of the coexisting α2, γ and τ phases after ageing for 10000 h. The Vickers microhardness decreases reaching a minimum after ageing for about 500 h and then increases to peak values with increasing ageing time. The ageing time longer than 1500 h leads to a continuous softening of the alloy at all ageing temperatures.K e y w o r d s : titanium aluminides, TiAl, phase identification, microstructure, diffraction

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Section: Effect Of Ageing On Microstructuresupporting

confidence: 56%

Long term microstructural stability of intermetallic Ti-46Al-8Ta alloy during ageing at temperatures of 700-800 °C

Lapin¹,

Pelachová²,

Staneková³

et al. 2010

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“…The weld tests have been carried out using the titanium aluminide alloys "GE" (Titanium-48Aluminium-2Chrome-2Niobium) and "V5" (Titanium-45.5Aluminium-5.5Niobium-0.2Chrome-0.2Boron) (phase diagrams in [4] und [5]). "GE" belongs to the second generation of titanium aluminide alloys.…”

Section: Materials and Experimental Detailsmentioning

confidence: 99%

“…The concentration reduction of aluminium and the relative accumulation of titanium has the result that the phase equilibrium in the binary phase diagram aluminium-titanium is shifting from the c-phase towards the a 2 -phase (compare: phase diagram in [4], [5]). Even in the case of indefinitely slow cooling, less c-phase may develop.…”

Section: Effects Of the Welding Parameters On The Weld Structurementioning

confidence: 99%

Electron beam welding of titanium aluminides – Influence of the welding parameters on the weld seam and microstructure

Reisgen

Olschok

Backhaus

2010

Materialwissenschaft Werkst

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This paper gives an account of research which has been carried out on electron-beam welded specimens made of high-Niobium c/a 2 -titanium aluminides in comparison to c-titanium aluminides. The high niobium content of this alloy (5 -8%) has a positive effect on the strength and the creep resistance and also on the oxidation resistance. The standard welding parameters weld speed and beam current and also additional beam oscillation have been used for the determination of factors which will effect the solidification morphology and structural constitution since those, in return, exert influence on the high cracking susceptibility of the alloy. In order to reduce the critical cooling rate, preheating which has a positive effect on crack formation has, in addition, been applied. In a direct comparison of both alloys, micrographs and electron beam micro-analyses of the developing weld structure and of the heat affected zone, the effects of the beam parameters on both alloys have been established.Keywords: Electron beam welding / microstructure / titanium aluminide / high temperature / Diese Veröffentlichung berichtet über Untersuchungen an Elektronenstrahl geschweißten Proben aus hochniobhaltigen c/a 2 -Titan-Aluminiden im Vergleich zu c-Titan-Aluminiden. Der hohe Niobgehalt dieser Legierung von 5 -8% wirkt sich positiv auf die Festigkeit und Kriechbeständigkeit sowie die Oxidationsbeständigkeit aus. Anhand der Standard-Schweißparameter Schweißgeschwindigkeit und Strahlstrom sowie zusätzlicher Strahlpendelung werden Einflussfaktoren auf die Erstarrungsmorphologie und Gefü-geausbildung bestimmt, die die hohe Rissanfälligkeit der Legierung beeinflussen. Zusätzlich wird eine Vorwärmung zur Reduzierung der kritischen Abkühlrate appliziert, die günstig auf die Rissvermeidung einwirkt. Im direkten Vergleich der zwei Legierungen werden durch Schliffbilder und Elektronenstrahlmikroanalysen des entstehenden Schweißgefüges und der Wärmeeinflusszone Auswirkungen der Strahlparameter auf die beiden Legierungen festgestellt.

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“…This could be the reason for the good flow ability of boron-containing TiAl alloy highly praised privately by some foundrymen [13]. With boron addition above lat% TiB 2 becomes the primary solidifying phase inTi-47.4Al [12]. The liquidus projection for Ti-Al-B system covering the Al range of 25-57at% was first proposed by Hymen, showing that the primary boride type varies with Al concentration [14].…”

Section: Impact To Tial Physical Metallurgymentioning

confidence: 97%

“…al [12]. Apart from some new phase fields related to titanium borides one of the most interesting outcomes is that boron addition lowers the liquidus, thus reducing the freezing range of Ti-47.4A1.…”

Section: Impact To Tial Physical Metallurgymentioning

confidence: 99%

A Quarter Century Journey of Boron as a Grain Refiner in TiAl Alloys

2014

Gamma Titanium Aluminide Alloys 2014

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The Al–B–Nb–Ti system

Cited by 267 publications

References 55 publications

Long term microstructural stability of intermetallic Ti-46Al-8Ta alloy during ageing at temperatures of 700-800 °C

Long term microstructural stability of intermetallic Ti-46Al-8Ta alloy during ageing at temperatures of 700-800 °C

Electron beam welding of titanium aluminides – Influence of the welding parameters on the weld seam and microstructure

A Quarter Century Journey of Boron as a Grain Refiner in TiAl Alloys

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