In situ study of phase transformations during laser-beam welding of a TiAl alloy for grain refinement and mechanical property optimization

Liu, Jie; Staron, Peter; Riekehr, Stefan; Stark, Andreas; Schell, Norbert; Huber, N.; Schreyer, A.; Müller, Martin; Kashaev, Nikolai

doi:10.1016/j.intermet.2015.03.003

Cited by 26 publications

(18 citation statements)

References 30 publications

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“…For this purpose, a sample environment was built that has since been used for various in situ LBW experiments. [170][171][172] The sample environment allows monitoring the phase content of the weld using HEXRD at the HZG-run synchrotron beamline P07 at DESY.…”

Section: Case Study Ii: Laser Beam Weldingmentioning

confidence: 99%

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Exploring Structural Changes, Manufacturing, Joining, and Repair of Intermetallic γ‐TiAl‐Based Alloys: Recent Progress Enabled by In Situ Synchrotron X‐Ray Techniques

et al. 2021

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Intermetallic titanium aluminides based on the ordered γ-TiAl phase fulfil many of the key requirements of lightweight high-temperature applications. In addition to a high melting point, high specific Young's modulus and strength at elevated temperatures, excellent creep properties, and a satisfactory oxidation and burn resistance, especially their low density of roughly 4 g cm À3 makes them a material of choice for challenging structural applications such as found, e.g., in environmentally friendly combustion engine options. [1][2][3][4] Capable of withstanding extreme conditions, γ-TiAl-based alloys have already entered service as low-pressure turbine blades in jet engines, such as the GEnx engine by GE Aviation, [5] the Geared Turbofan (GTF) engine by Pratt and Whitney, [6] as well as the LEAP engine by CFM International, a joint company between Safran Aircraft Engines and GE. [7,8] In these applications, γ-TiAl-based turbine blades substitute some of the blades made of twice as heavy Ni-base superalloys in a temperature range up to 750 °C. The implementation of the advanced, lightweight material, which is also attended by an adaptation of the design, entails a substantial reduction in weight, fuel consumption, and CO 2 and NO x emissions. [9] Apart from the aircraft engine industry, γ-TiAl-based alloys have also found applications in the automotive industry, e.g., as engine valves in sports and racing cars or as turbocharger turbine wheels. [1,3,[10][11][12][13][14] The past few decades have witnessed great efforts to develop intermetallic γ-TiAl-based alloy systems that are suitable for service in these demanding areas while being economically competitive at the same time. To this end, various alloy compositions and processing routes have been studied intensively. [1,[15][16][17][18][19][20][21] Recent progress has been reviewed, e.g., in the works by Appel et al., Clemens et al., and Mayer et al. [1,3,9,22] Due to the complexity of the intermetallic alloy system, which encompasses a multitude of phases and phase transformations, [23] purposeful alloy design requires the use of manifold characterization methods. Diffraction and scattering techniques, in particular, offer access to the atomic structure of the material and provide insights into a variety of microstructural parameters. [24][25][26][27] High-energy X-rays, such as available at today's synchrotron radiation sources, and recent developments in hardware technology nowadays allow to conduct so-called in situ experiments. Experiments of this kind reveal-at a high temporal resolution-the relationship between selected external

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Section: Case Study Ii: Laser Beam Weldingmentioning

confidence: 99%

mentioning

confidence: 99%

Exploring Structural Changes, Manufacturing, Joining, and Repair of Intermetallic γ‐TiAl‐Based Alloys: Recent Progress Enabled by In Situ Synchrotron X‐Ray Techniques

et al. 2021

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“…interest. In the literature, several in situ studies of solidification in TiAl alloys have been published, which, e.g., were devoted to levitation melting, [16] laser welding, [17][18][19] brazing, [19,20] or additive manufacturing. [21] However, in situ studies of directional solidification in which the solidification conditions are clearly defined and can be varied during the experiment have, to date, not been reported according to the knowledge of the authors.…”

Section: Introductionmentioning

confidence: 99%

An In Situ High‐Energy Synchrotron X‐Ray Diffraction Study of Directional Solidification in Binary TiAl Alloys

et al. 2021

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Phase formation and microstructure selection during solidification in γ‐TiAl alloys are highly relevant, both with respect to the microstructure and texture of cast alloys and to directional solidification, which allows to obtain a unique combination of properties. However, during cooling to room temperature, the solidifying phases transform to low‐temperature phases, which mask the prior situation during solidification. A new inductive crucible‐free zone melting furnace is used in this work, which is specially designed for in situ investigations of solidification using synchrotron radiation. Herein, alloys with 45 and 48 at% Al are studied, and it can be shown that with varying withdrawal rate, a change from α solidification to synchronous β + α solidification occurs in Ti–48Al, as it is predicted in the literature. Furthermore, it is observed that by increasing the withdrawal rate, a preferred <001> growth of the β phase occurs in alloys with 45 at% Al, which is interpreted as a transition to dendritic solidification. The observations are compared with a microstructure selection map calculated according to the nucleation and constitutional undercooling (NCU) model proposed in the literature.

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“…Fast detectors (up to 20 kHz) have been employed to examine phase evolution under rapid processing [10,[15][16][17][18][19][20][21][22], such as welding and AM processing, and combination with ultrafast imaging provided new insights into the AM process [9,18,22]. Studies with high angular resolution and a relatively large area detector have revealed details of lattice changes for external mechanical and temperature factors [11,[23][24][25][26][27][28]. Our recent report presented an in-situ study of Ni-alloy 718 with a multi-panel area detector with an unprecedented combination of high 2θ-angular resolution and a 250 Hz frame rate [29].…”

Section: Introductionmentioning

confidence: 99%

High speed synchrotron X-ray diffraction experiments resolve microstructure and phase transformation in laser processed Ti-6Al-4V

Lim

Aroh

et al. 2021

Materials Research Letters

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In situ study of phase transformations during laser-beam welding of a TiAl alloy for grain refinement and mechanical property optimization

Cited by 26 publications

References 30 publications

Exploring Structural Changes, Manufacturing, Joining, and Repair of Intermetallic γ‐TiAl‐Based Alloys: Recent Progress Enabled by In Situ Synchrotron X‐Ray Techniques

Exploring Structural Changes, Manufacturing, Joining, and Repair of Intermetallic γ‐TiAl‐Based Alloys: Recent Progress Enabled by In Situ Synchrotron X‐Ray Techniques

An In Situ High‐Energy Synchrotron X‐Ray Diffraction Study of Directional Solidification in Binary TiAl Alloys

High speed synchrotron X-ray diffraction experiments resolve microstructure and phase transformation in laser processed Ti-6Al-4V

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