Effect of carbon addition on solidification behavior, phase evolution and creep properties of an intermetallic β-stabilized γ-TiAl based alloy

Schwaighofer, Emanuel; Rashkova, Boryana; Clemens, Helmut; Stark, Andreas; Mayer, Svea

doi:10.1016/j.intermet.2013.11.011

Cited by 146 publications

(117 citation statements)

References 47 publications

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“…Quantitative metallographic analysis revealed that the lamellar grains contained about 37 vol.% of the α 2 -phase and 63 vol.% of the γ-phase. These results are in good agreement with the results reported by Schwaighofer et al [13] that the content of α 2 -phase was just below 40 % for the TNM alloy (Ti--43.5Al-4Nb-1Mo-0.1B) with 0.75 C (at. %) after HIP at 1200…”

Section: Characterization Of Microstructure and Mechanical Propertiessupporting

confidence: 93%

“…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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Section: Characterization Of Microstructure and Mechanical Propertiessupporting

confidence: 93%

Section: Characterization Of Microstructure and Mechanical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Čegan¹,

Szurman²

2018

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“…This increase of the microhardness is caused by carbon solid solution strengthening of the α 2 phase, because the γ phase has low solubility limit and precipitation of small carbide particles in this phase does not significantly affect the microhardness [40]. Similar effect of carbon on microhardness was also observed by Schweighofer et al [43] in TNM alloy. The differences in microhardness are also caused by different alloying elements.…”

Section: Microstructuresupporting

confidence: 69%

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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Advanced Intermetallic Titanium Aluminides

Clemens

Smarsly

Güther³

et al. 2016

Proceedings of the 13th World Conference on Titanium

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After almost four decades of intensive fundamental research and development activities intermetallic titanium aluminides have found application in aircraft and automotive engines. The advantage of this class of innovative high-temperature materials is their low density in combination with good strength and creep properties up to 800°C. A drawback, however, is their limited ductility at room temperature, which is reflected in a low plastic fracture strain. Advanced engineering TiAl alloys are complex multi-phase materials which can be processed by ingot or powder metallurgy, precision casting methods as well as additive manufacturing, e.g. electron beam melting. Each production process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and/or subsequent heat-treatments. The aim of these heat-treatments is to provide a microstructure with balanced mechanical properties, i.e. sufficient ductility at room temperature as well as creep strength at elevated temperature. In order to achieve this goal, the knowledge of the occurring solid state phase transformations including order/disorder reactions is essential. Therefore, thermodynamic calculations were conducted at first to predict the phase diagram of engineering TiAl alloys. After experimental verification, these phase diagrams provided the basis for the development of the heat-treatments mentioned above. To account the influence of deformation and kinetic aspects sophisticated ex-and in-situ methods have been employed to investigate the evolution of the microstructure during thermo-mechanical processing and subsequent heat-treatments. For example, in-situ high-energy Xray diffraction was conducted to study dynamic recovery and recrystallization processes during hot-deformation tests. Summarizing all results a consistent picture regarding processing and mechanical properties of advanced engineering TiAl alloys can be given.

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Effect of carbon addition on solidification behavior, phase evolution and creep properties of an intermetallic β-stabilized γ-TiAl based alloy

Cited by 146 publications

References 47 publications

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

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

Advanced Intermetallic Titanium Aluminides

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