Relationships between interstitial content, microstructure and mechanical properties in fully lamellar Ti–48Al alloys, with special reference to carbon

Perdrix, F.; Trichet, M.-F.; Bonnentien, J.-L.; Cornet, Muriel; Bigot, J.

doi:10.1016/s0966-9795(01)00066-8

Cited by 70 publications

(28 citation statements)

References 26 publications

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“…The change of both the lattice parameters of the γ M and γ phases during the precipitation of α/α 2 laths and subsequent long-term ageing (Fig. 7a) can be attributed to the redistribution of alloying elements, mainly to an increase of Al content in the γ phase [15][16][17].…”

Section: 3mentioning

confidence: 99%

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: 3mentioning

confidence: 99%

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 relatively high volume fraction of the α 2 -phase can be explained by a stabilizing effect of carbon on the α 2 -phase and relatively high cooling rate [10,13,14]. Figure 1d shows TEM bright field image of the alloy after HT.…”

Section: Characterization Of Microstructure and Mechanical Propertiesmentioning

confidence: 99%

“…Several studies have been focused on the improvement of mechanical properties and creep resistance in the carbon-doped TiAl alloys, and it has been proven that improvement of mechanical properties relates to the solid solution hardening and precipitation hardening [13][14][15][16][17][18][19][20][21][22]. Also, the addition of carbon to lamellar TiAl--based alloys can also reduce lamellar space effectively [19].…”

Section: Introductionmentioning

confidence: 99%

“…The driving force for the precipitation process is the limited solubility of carbon, and as generally observed on other alloys, the shape, size and distribution of precipitates are the main factors determining the mechanical properties. In spite of the previous studies which dealt with precipitation of carbides in TiAl alloys [10,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], information about the microstructural stability of carbon added alloys at higher temperatures and longer times is still lacking in the literature. Therefore, this article aims to study the long-term microstructural stability of the Ti-45Al--5Nb-0.2B-0.75C (at.%) alloy and effect of microstructural changes on mechanical properties during longterm ageing at temperatures of 750, 850 and 950…”

Section: Introductionmentioning

confidence: 99%

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Thermal stability and precipitation strengthening of fully lamellar Ti-45Al-5Nb-0.2B-0.75C alloy

Čegan¹,

Szurman²

2018

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The alloy with a composition Ti-45Al-5Nb-0.2B-0.75C (at.%) was prepared by induction melting and centrifugal casting. The fully lamellar microstructure of the alloy without carbides was produced by heat treatment consisting of hot isostatic pressing (HIP) and solution annealing followed by cooling to room temperature. The stability of the fully lamellar γ(TiAl) + α2(Ti3Al) microstructure was studied at temperatures of 750, 850 and 950• C up to an ageing time of 3400 h. The microstructure analysis shows that the most dominant change in the microstructure was the α2 lamellae thinning, which was more pronounced at a higher ageing temperature and longer time. The formation of recrystallized γ grains and Ti2AlC carbides was observed during ageing at the temperatures of 850 and 950• C. The microstructural changes affected the microhardness at room temperature (RT) and compression yield strength at temperatures ranging from RT to 950K e y w o r d s : titanium aluminides, thermal stability, microstructure, carbides, yield strength

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“…The carbides are found mainly in the γ lamellae and in the interdendritic γ phase. Their small size indicates that they were formed by precipitation from the solid γ phase as a result of low solubility of interstitial carbon in TiAl (up to 0.02-0.03 at.%) [40]. No fine carbides have been observed in the α 2 phase, which shows much higher solubility of C than that of the γ phase (up to 0.9 at.%).…”

Section: Microstructurementioning

confidence: 99%

Preparation of TiAl-based alloys by induction melting in graphite crucibles

Čegan¹,

Szurman²,

Kursa³

et al. 2016

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Three TiAl-based alloys with nominal composition Ti-47Al-8Nb, Ti-47Al-8Ta and Ti-47Al--8Ta-0.3Y (at.%) were prepared by induction melting in graphite crucibles and centrifugal casting into graphite moulds. Chemical composition, microstructure and mechanical properties of the as-cast alloys are characterised. The melting in the graphite crucible leads to an increase of carbon content from 460 to 1020 wtppm and formation of fine carbide particles predominantly in the γ(TiAl) phase. Beside fine carbides, the addition of 0.3 at.% of yttrium results in formation of fine Y2O3 and YAl2 particles. The oxygen content depends on the chemical composition and varies between 330 and 780 wtppm for Ta and Nb containing alloys, respectively. The as-cast alloys exhibit relatively high values of room-temperature compression yield strength up to 922 MPa, ultimate compression strength up to 1793 MPa and plastic deformation to fracture up to 24.3 %. The compression yield strength increases linearly with increasing Vickers microhardness of the as-cast alloys. From the point of view of chemical composition, microstructure and studied mechanical properties, induction melting in the graphite crucible and centrifugal casting into graphite mould can be considered as a suitable method of preparation of TiAl-based alloys.K e y w o r d s :

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Relationships between interstitial content, microstructure and mechanical properties in fully lamellar Ti–48Al alloys, with special reference to carbon

Cited by 70 publications

References 26 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

Thermal stability and precipitation strengthening of fully lamellar Ti-45Al-5Nb-0.2B-0.75C alloy

Preparation of TiAl-based alloys by induction melting in graphite crucibles

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