The transient liquid phase bonding process of a γ-TiAl alloy with brazing solders containing Fe or Ni

Hauschildt, Katja; Stark, Andreas; Schell, Norbert; Müller, Martin; Pyczak, Florian

doi:10.1016/j.intermet.2018.12.004

Cited by 17 publications

(8 citation statements)

References 24 publications

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“…[177] After 19 h at brazing temperature, the microstructure in the joint region consists of several layers, which show phase compositions similar to the ones following previous ex situ experiments. [175,177,178] Now, the stepwise formation of these layers and their differentiation over time was directly monitored during processing.…”

Section: Case Study Iii: Transient Liquid Phase Bondingmentioning

confidence: 99%

“…Based on the known phase diagrams, however, it was not possible to explain the microstructure formation. [ 175 ] Thus, for a better understanding of the bonding process, the phase formation and the phase distribution over the brazing zone were investigated time and position resolved during the bonding process using HEXRD at the synchrotron radiation facility PETRA III at DESY.…”

Section: Rebuilding Processing Conditions In the Labmentioning

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 Iii: Transient Liquid Phase Bondingmentioning

confidence: 99%

Section: Rebuilding Processing Conditions In the Labmentioning

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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“…With the increasing use of γ-TiAl in aircraft turbines, the need for repair or modification solutions will increase, irrespective of the original production route of the components concerned. Currently, the research is performed on transient liquid phase (TLP) bonding for the repair of γ-TiAl, using Fe or Ni as melting point depressing elements (MPD) [ 13 ]. Furthermore, in the recently completed LuFo-project (FKZ 20T1526A), the diffusion welding of TiAl was investigated with, again, the aim of the repair.…”

Section: Introductionmentioning

confidence: 99%

Direct Energy Deposition of TiAl for Hybrid Manufacturing and Repair of Turbine Blades

et al. 2020

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While repair is mainly used to restore the original part geometry and properties, hybrid manufacturing aims to exploit the benefits of each respective manufacturing process regarding either processing itself or resulting part characteristics. Especially with the current implementation of additive manufacturing in the production of TiAl, turbine blades for both hybrid manufacturing and repair new opportunities are enabled. One main issue is the compatibility of the two or more material types involved, which either differ regarding composition or microstructure or both. In this study, a TNMTM-alloy (Ti-Nb-Mo) was manufactured by different processes (casting, forging, laser additive manufacturing) and identically heat-treated at 1290 °C. Chemical compositions, especially aluminum and oxygen contents, were measured, and the resulting microstructures were analyzed with Scanning Electron Microscopy (SEM) and High-energy X-ray diffraction (HEXRD). The properties were determined by hardness measurements and high-temperature compression tests. The comparison led to an overall assessment of the theoretical compatibility. Experiments to combine several processes were performed to evaluate the practical feasibility. Despite obvious differences in the final phase distribution caused by deviations in the chemical composition, the measured properties of the samples did not differ significantly. The feasibility of combining direct energy deposition (DED) with either casting or laser powder bed fusion (LPBF) was demonstrated by the successful build of the dense, crack-free hybrid material.

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The transient liquid phase bonding process of a γ-TiAl alloy with brazing solders containing Fe or Ni

Cited by 17 publications

References 24 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

Direct Energy Deposition of TiAl for Hybrid Manufacturing and Repair of Turbine Blades

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