Refinement of the lamellar structure in TiAl-BASED intermetallic compound by addition of carbon

Park, Hyun Soon; Nam, Soo Woo; Kim, Nack J.; Hwang, Sun Keun

doi:10.1016/s1359-6462(99)00266-3

Cited by 65 publications

(34 citation statements)

References 14 publications

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“…It is well known that grain refinement is an effective method to improve the tensile properties of TiAl-based alloys. For this purpose, the addition of C is an effective means, as reported by Park et al [24,26] The employment of Y, according to the result of the present work, leads to an additional microstructural refinement. The grain-refining effect of Y is attributed to the oxides that were formed prior to extrusion.…”

Section: Discussionsupporting

confidence: 77%

“…This refinement was in addition to that by the C addition to the TiAl-Mn-Mo composition, reported earlier by Park et al [24,26] In the The average concentration of oxygen in the samples was approximately 1500 ppm regardless of the compositions. solution-treated condition (1400°C/1 hour and air cooled), the TiAl-1.4Mn-2Mo-0.3C* alloy showed an average grain and, apparently, cannot be solved by subsequent heat treatments.…”

Section: A Microstructuressupporting

confidence: 71%

“…[22][23][24][25][26]30,31] Figure 1 shows scanning electron microscope (SEM) micrographs of elemental powders used in experimental alloys. The mean size of powder particles of Ti, Al, Mn, Mo, C, and Y ranged from 7 to 74 m. The chemical compositions, nominal and analyzed, of the experimental alloys are given in Table I.…”

Section: Methodsmentioning

confidence: 99%

“…[21] Recently, Hwang et al reported the beneficial effect of a C addition: carbon atoms refined the microstructure in terms of the colony size as well as the lamellar spacing in a fully lamellar structure, thereby improving the high-temperature strength of a fully lamellar TiAl alloy produced by elemental powder metallurgy (EPM). [22][23][24][25][26] Two of the main obstacles in commercializing the TiAl alloy are the mechanical properties at the application temperatures and the weak oxidation resistance of the alloy in a high-temperature air environment. In this respect, the detrimental effect of oxygen is twofold: internal oxygen is a culprit of embrittlement, and external oxygen in air is responsible for surface degradation.…”

Section: Introductionmentioning

confidence: 99%

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Development and elemental powder metallurgy of a Y-containing two-phase TiAl alloy

Hwang

Morris

2003

Metall Mater Trans A

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The Y modification of a two-phase (␥ ϩ ␣ 2 ) TiAl-(Mn,Mo,C) alloy was studied with an aim to improve, mainly, the oxidation resistance and the mechanical properties in a high-temperature air environment. The experimental alloy was prepared by the elemental powder metallurgy (EPM) method. The addition of up to 0.6 at. pct Y resulted in a significant improvement in tensile properties and compressive yield strength and an anomalous yielding phenomenon withal. Two structural characteristics were identified: first, microstructural refinement in terms of the grain size as well as the interlamellar spacing, and second, precipitation of fine oxides that might scavenge harmful oxygen. Deformation was found to be mainly provided by 1/2͗110] ordinary dislocations and a much lesser amount of ͗011] superdislocations as compared to what has been reported in other (␥ ϩ ␣ 2 ) TiAl alloys. The oxidation resistance of the experimental alloy was evaluated by air-exposure tests at 800°C, from which the oxidation kinetics and the morphological and phase characteristics of the oxide scales were analyzed. With a Y addition, the constituents of the oxide scale changed from those of the Y-free alloy. In the case of the Y-free alloy, the oxide scale which formed upon extended air exposure (350 hours) at 800°C consisted of a mixture of TiO 2 and ␣-Al 2 O 3 . In the case of the alloy modified with Y (0.6 at. pct), however, the oxide scale formed in an identical environment was considerably different: it consisted of a complex mixture of

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Section: Discussionsupporting

confidence: 77%

Section: A Microstructuressupporting

confidence: 71%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development and elemental powder metallurgy of a Y-containing two-phase TiAl alloy

Hwang

Morris

2003

Metall Mater Trans A

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“…In high Nb-and Mo-containing alloys, solid solution hardening has been shown to be a dominating hardening effect in the γ-TiAl phase. Furthermore, the alloying elements Nb and Mo have been shown to reduce diffusivity and retard thermally-activated dislocation climb during creep [88]. Below their solubility limit, a solid solution hardening effect is also attributed to additions of C and N, albeit these elements are solved interstitially [40,41,89].…”

Section: Recent Advancements In the Alloy Development: The Introductimentioning

confidence: 99%

In Situ Characterization Techniques Based on Synchrotron Radiation and Neutrons Applied for the Development of an Engineering Intermetallic Titanium Aluminide Alloy

Erdely

Schmoelzer

Schwaighofer

et al. 2016

Metals

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Abstract:Challenging issues concerning energy efficiency and environmental politics require novel approaches to materials design. A recent example with regard to structural materials is the emergence of lightweight intermetallic TiAl alloys. Their excellent high-temperature mechanical properties, low density and high stiffness constitute a profile perfectly suitable for their application as advanced aero-engine turbine blades or as turbocharger turbine wheels in next-generation automotive engines. As the properties of TiAl alloys during processing as well as during service are dependent on the phases occurring, detailed knowledge of their volume fractions and distribution within the microstructure is of paramount importance. Furthermore, the behavior of the individual phases during hot deformation and subsequent heat treatments is of interest to define reliable and cost-effective industrial production processes. In situ high-energy X-ray diffraction methods allow tracing the evolution of phase fractions over a large temperature range. Neutron diffraction unveils information on order-disorder transformations in TiAl alloys. Small-angle scattering experiments offer insights into the materials' precipitation behavior. This review attempts to shine a light on selected in situ diffraction and scattering techniques and the ways in which they promoted the development of an advanced engineering TiAl alloy.

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Design, Processing, Microstructure, Properties, and Applications of Advanced Intermetallic TiAl Alloys

2012

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After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ‐TiAl phase have found applications in automotive and aircraft engine industry. The advantages of this class of innovative high‐temperature materials are their low density and their good strength and creep properties up to 750 °C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi‐phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo‐mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e., concurrent increase of ductility at room temperature and creep strength at elevated temperature. This review gives a general survey of engineering γ‐TiAl based alloys, but concentrates on β‐solidifying γ‐TiAl based alloys which show excellent hot‐workability and balanced mechanical properties when subjected to adapted heat treatments. The content of this paper comprises alloy design strategies, progress in processing, evolution of microstructure, mechanical properties as well as application‐oriented aspects, but also shows how sophisticated ex situ and in situ methods can be employed to establish phase diagrams and to investigate the evolution of the micro‐ and nanostructure during hot‐working and subsequent heat treatments.

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Refinement of the lamellar structure in TiAl-BASED intermetallic compound by addition of carbon

Cited by 65 publications

References 14 publications

Development and elemental powder metallurgy of a Y-containing two-phase TiAl alloy

Development and elemental powder metallurgy of a Y-containing two-phase TiAl alloy

In Situ Characterization Techniques Based on Synchrotron Radiation and Neutrons Applied for the Development of an Engineering Intermetallic Titanium Aluminide Alloy

Design, Processing, Microstructure, Properties, and Applications of Advanced Intermetallic TiAl Alloys

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