Phase Equilibria and Phase Transformations in Molybdenum-Containing TiAl Alloys

Mayer, Svea; Sailer, Christian; Nakashima, Hideharu; Schmoelzer, Thomas; Lippmann, Thomas; Staron, Peter; Liss, Klaus-Dieter; Clemens, Helmut; Takeyama, Masao

doi:10.1557/opl.2011.31

Cited by 18 publications

(7 citation statements)

References 10 publications

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“…1(a)]. Concerning the evolution of the microstructure during solidification, HIPing, short, and long‐term ageing treatments further investigations are underway and will be published in a forthcoming paper 23…”

Section: Resultsmentioning

confidence: 99%

In Situ Diffraction Experiments for the Investigation of Phase Fractions and Ordering Temperatures in Ti‐44 at% Al‐(3‐7) at% Mo Alloys

et al. 2010

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During the last 20 years, research and development efforts have been undertaken to develop g-TiAl based alloys as a replacement for Ni-based superalloys for high-temperature applications in turbine blades of advanced aero engines and turbo-chargers of automotive combustion engines. [1] Intermetallic g-TiAl based alloys are intended for use in the temperature range from 600 to 900 8C and there is growing demand for alloys which can be deformed easily by cost-effective forming operations. One possible approach is to design alloys with microstructures in which homogenously distributed b and g-phase are the main constituents. [2] Therefore, these alloys are named b/g-alloys.[3] Since Mo is a strong b stabilizer the ternary system Ti-Al-Mo is well suited for studying this type of alloys. [4] Despite the importance of Mo as an alloying element, the knowledge of its effect on phase diagram, transformation temperatures, and order/ disorder transition temperatures is limited. In many advanced multi-phase TiAl alloys three intermetallic phases, g, a 2 , and b o , are the dominating microstructural constituents, all of which are ordered at room temperature. At elevated temperatures the ordered hexagonal a 2 -phase (D0 19 ) disorders to a (A3) and the ordered cubic b o -phase (B2) disorders to the body-centered cubic b-phase (A2) while the g-phase (L1 0 ) remains ordered up to its dissolution temperature (T g ). The phase fractions present have a strong influence on the mechanical properties of the material and on the processing characteristics at hot-working temperatures. High b/b o -phase contents, for instance, improve the deformation behavior during hot-working but simultaneously decrease the creep resistance if prevailing at service temperature. [5] Additionally, the room temperature ductility is negatively affected by high b o -phase fractions. [6] In the present work, sections of the ternary phase diagram Ti-Al-Mo, obtained by thermodynamic calculations and COMMUNICATION Being a strong b stabilizer, Mo has gained importance as an alloying element for so-called b/g-TiAl alloys. Intermetallic TiAl-based alloys which contain a significant volume fraction of the body-centered cubic b-phase at elevated temperatures have proven to exhibit good processing characteristics during hot-working. Unfortunately, the effect of Mo on the appearing phases and their temperature dependence is not well known. In this work, sections of the Ti-Al-Mo ternary phase diagram derived from thermodynamic calculations as well as experimental data are presented. The phase transition temperatures stated in these phase diagrams are compared with the results of high-temperature diffraction studies using high-energy synchrotron radiation. Additionally, the disordering temperature of the b o -phase is determined. 306 wileyonlinelibrary.com ß

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Section: Resultsmentioning

confidence: 99%

In Situ Diffraction Experiments for the Investigation of Phase Fractions and Ordering Temperatures in Ti‐44 at% Al‐(3‐7) at% Mo Alloys

et al. 2010

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“…[14] Details on ingot production, phase diagram and original microstructure can be found in. [6,7] Diffraction experiments were conducted with a beam of monochromatic synchrotron radiation which had a mean energy of 100 keV and a cross-section of 1x1 mm 2 . Heating of the cylindrical specimens with a diameter of 5 mm and a length of 15 mm was performed by a modified Bähr DIL 805A/D dilatometer.…”

Section: Methodsmentioning

confidence: 99%

“…The phases occurring in this alloy were studied by means of in-situ high-energy X-ray diffraction (HEXRD) over a wide temperature range [6] and it was attempted to construct a phase diagram from the results of this study and information published in the literature. [7] In technological processes, however, high heating and cooling rates are frequently used. Therefore, the materials behavior under disequilibrium conditions is investigated in the current study.…”

Section: Introductionmentioning

confidence: 99%

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In Situ Synchrotron Study of B19 Phase Formation in an Intermetallic γ‐TiAl Alloy

et al. 2012

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“…In this short review representative sections of the ternary Ti-Al-Mo phase diagram derived from thermodynamic calculations and experimental results are presented 3,4 . In principle most advanced multi-phase TiAl alloys consist of three intermetallic phases, namely α 2 -Ti 3 Al, β o -TiAl and γ-TiAl, which are all ordered at ambient temperature.…”

Section: Introductionmentioning

confidence: 99%

On Phase Equilibria and Phase Transformations in β/γ-TiAl Alloys – A Short Review

Mayer

Sailer

Schmoelzer

et al. 2011

Berg Huettenmaenn Monatsh

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stabilizer it plays an important role among TiAl-based alloys, especially since a significant volume fraction of the disordered body-centered cubic β-phase improves the processing characteristics during hot-working at elevated temperatures. Unfortunately the effect of Mo on the individual phases and their transition temperatures is insufficiently known though it is essential for designing engineering components. In this paper sections of the Ti-Al-Mo ternary phase diagram derived from thermodynamic calculations as well as experimental data are presented. Furthermore the effect of Mo on the phase transformation behavior during slow heating and rapid cooling in the course of isothermal short and long-term heat treatments is elaborated. Below a certain amount of Mo the high-temperature cubic β-phase transforms into ordered hexagonal α 2 '-martensite during water quenching. At higher contents the high-temperature β-phase can be retained upon quenching; only the ordering reaction β → β o takes place. The subsequent tempering at 1000 °C leads to a strong grain refinement as well as to a reduction in hardness.

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Phase Equilibria and Phase Transformations in Molybdenum-Containing TiAl Alloys

Cited by 18 publications

References 10 publications

In Situ Diffraction Experiments for the Investigation of Phase Fractions and Ordering Temperatures in Ti‐44 at% Al‐(3‐7) at% Mo Alloys

In Situ Diffraction Experiments for the Investigation of Phase Fractions and Ordering Temperatures in Ti‐44 at% Al‐(3‐7) at% Mo Alloys

In Situ Synchrotron Study of B19 Phase Formation in an Intermetallic γ‐TiAl Alloy

On Phase Equilibria and Phase Transformations in β/γ-TiAl Alloys – A Short Review

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