Carbide precipitation in γ-TiAl alloys

Chen, S.; Beaven, P. A.; Wagner, Richard

doi:10.1016/0956-716x(92)90564-u

Cited by 66 publications

(35 citation statements)

References 3 publications

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“…None of the applied techniques give any indication for the formation of C-containing precipitates as a result of the applied heat treatment. This is in agreement with the results of Chen et al who also detected no precipitates in Ti-48Al-2Nb-0.2C alloys after a heat treatment of 1100°C for 1-2 hours followed by water-quenching [13].…”

Section: Discussionsupporting

confidence: 83%

“…Earlier TEM studies [12,13,16,17] have revealed typical C-containing precipitates of 20 -100 nm in length and 3-6 nm in width, which form arrays with a spacing of about 50-100nm. If a similar distribution was present in our material, we would have detected several precipitates within our analysed APT volume as well as observing them in the TEM, e.g.…”

Section: Discussionmentioning

confidence: 99%

“…In the particular case of C the effect is beneficial due to both solid-solution hardening and formation of Ccontaining precipitates [12]. These are either cubic Ti 3 AlC Perovskite-phase ("P"-phase) or hexagonal Ti 2 AlC-phase ("H"-phase) precipitates which form depending on thermal treatment and aging conditions [12,13]. Typical agehardening behaviour is observed where the strength is increasing with the formation of precipitates [12,14,15].…”

Section: Introductionmentioning

confidence: 98%

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High carbon solubility in a γ-TiAl-based Ti–45Al–5Nb–0.5C alloy and its effect on hardening

et al. 2009

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The C distribution within the -TiAl-phase of a Ti-45Al-5Nb-0.5C alloy with near- microstructure has been studied by atom probe tomography. In most areas the C atoms are homogenously distributed, and only a few C enriched features were detected which are presumably Cottrell atmospheres surrounding dislocation cores. The C concentration within the -phase was measured to be approximately 0.25 at.%, which is a factor of ten higher than the solubility limit reported for other TiAl alloys. The reason for this unusually high C solubility is explained by an existing model which relates the number of octahedral sites consisting of six Ti atoms to the solubility limit of interstitials. The large amount of C in solid-solution can explain the results of a recent study which showed that the C-containing alloy had an approximately 30% increase in yield strength when compared with a C-free sheet containing the same Ti, Al and Nb concentration.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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High carbon solubility in a γ-TiAl-based Ti–45Al–5Nb–0.5C alloy and its effect on hardening

et al. 2009

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“…It was also found from the microscopic analysis that the long axis of Ti 3 AlC was parallel to the [001] direction of the γ-TiAl matrix and of a single variant. The orientation relationship between the Ti 3 AlC and γ-TiAl phase was confirmed to be of a cubic relationship, namely, (001) p // (001)γ and [010] p / /[010]γ, which accorded with the results of Tian and Nemoto [13] and S. Chen et al [27].…”

Section: Formation Of P-phase and H-phase In Epm Tial-based Alloysupporting

confidence: 88%

O-phase and carbides precipitation in intermetallics based on Ti−Al

Hwang

2001

Met. Mater. Int.

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In Ti-Al based intermetallics, precipitates of several ternary phases, such as the orthorhombic O-phase, perovskite P-phase and hexagonal H-phase structures, were experimentally identified during aging. These phases are believed to develop from the matrix of the α 2 -phase as a result of the characteristic diffusion of the alloying elements that involves changes in chemical composition and lattice structure. In this paper, the formation mechanism of these phases was studied in the matrix of Ti-Al-based intermetallic compounds. The O-phase was found to form in the primary equiaxed α 2 grains in multivariant forms and as fine α 2 +O mixtures in Ti-24Al-14Nb-3V-0.5Mo alloy during solution treatment at 1000 o C/1h followed by water quenching and aging at 650 o C and 850 o C. The supersaturation of Nb, the β stabilizer, resulted in a segregation of the Nbrich region and Nb-poor region, incurring the formation of the O-phase as a consequence of the α 2 -phase decomposition. A crystallographic orientation relationship between the α 2 -phase and the O-phase was observed. In Ti-46.6Al-2Mn-1.4Mo-0.3C alloy, P-phase carbides formed mainly at the α 2 /γ interface whereas some Hphase carbides were also found within the γ grain and at prior α grain boundaries. The presence of ledges between the P-phase and α 2 -phase interfaces indicated that the nucleation stage of the P-phase involved an interface-controlled process with a coherency relationship at the interface.

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“…[2] This manuscript presents theoretical calculations of properties of the interface with ␥-TiAl of the two carbide phases that have been observed experimentally to occur in C-doped alloys. [3] One of these is the perovskite-structure Ti 3 AlC, referred to as P-type, and the other is the hexagonal (H-type) phase Ti 2 AlC. Another ternary hexagonal phase, Ti 3 AlC 2 , is mentioned in the literature.…”

Section: Numerous Dopants Have Been Added To Two-phasementioning

confidence: 98%

Theory of interface properties for carbide precipitates in TiAl

Benedek

Seidman

Woodward

2003

Metall Mater Trans A

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Among the additives to TiAl alloys that have been investigated in recent years with the objective of improving high-temperature mechanical properties, particular attention has been given to carbon, which forms the carbide precipitates Ti 3 AlC (cubic perovskite) and Ti 2 AlC (hexagonal). Using the first-principles density-functional-theory code VASP, calculations of host-precipitate interface energies were performed for these two carbides. Calculations were first applied to coherent interfaces to determine the favored termination layers and parallel translation states. For the favored interface configurations, a correction is applied for the effect of misfit, to obtain an estimated interface energy for semicoherent interfaces. The correction is based on an approximate formulation recently presented by the authors. The perovskite is found to have a lower interface energy than the hexagonal phase, consistent with the experimental finding that the former nucleates homogeneously and the latter inhomogeneously.

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Carbide precipitation in γ-TiAl alloys

Cited by 66 publications

References 3 publications

High carbon solubility in a γ-TiAl-based Ti–45Al–5Nb–0.5C alloy and its effect on hardening

High carbon solubility in a γ-TiAl-based Ti–45Al–5Nb–0.5C alloy and its effect on hardening

O-phase and carbides precipitation in intermetallics based on Ti−Al

Theory of interface properties for carbide precipitates in TiAl

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