Stability of lamellar microstructures in a Ti–48Al–2Nb–2Cr alloy during heat treatment and its application to lamellae alignment as a quasi-seed

Du, Yajie; Shen, Jun; Xiong, Yi; Shang, Zhao; Fu, Hengzhi

doi:10.1016/j.intermet.2015.02.018

Cited by 16 publications

(8 citation statements)

References 22 publications

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“…Similar to the solving method of the solute redistribution in the melt, the solute concentration in the feed crystal (L ≤ x < ∞) is given by solving the Equation (5), which is subject to the boundary conditions of Equations ( 6)-( 8):…”

Section: Solute Redistribution In the Steady Statementioning

confidence: 99%

“…Float zone techniques, such as the optical float zone (OFZ) [1][2][3] and the electromagnetic confinement and directional solidification (EMCDS) [4,5], have been successfully employed to obtain non-contamination samples of TiAl alloys. However, simple directional solidification usually produces the worst samples in which the lamellar microstructures are inclined or normal to the growth direction [6].…”

Section: Introductionmentioning

confidence: 99%

“…However, simple directional solidification usually produces the worst samples in which the lamellar microstructures are inclined or normal to the growth direction [6]. To obtain the desired lamellar microstructure with excellent mechanical properties, the seeding method has been developed to align the lamellar microstructure by the float zone techniques [4,5,7]. In terms of the preparation and application of the seed materials, the present seeding methods can be categorized into two types: general seeding process [4,7] and quasi-seeding process [5].…”

Section: Introductionmentioning

confidence: 99%

“…To obtain the desired lamellar microstructure with excellent mechanical properties, the seeding method has been developed to align the lamellar microstructure by the float zone techniques [4,5,7]. In terms of the preparation and application of the seed materials, the present seeding methods can be categorized into two types: general seeding process [4,7] and quasi-seeding process [5]. For the general seeding process, because the primary phase of the seed alloy is α whereas that of the master alloy is usually β, there exists a large composition difference between them.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Solute Redistribution on Seeding Process of TiAl Alloys with Limited Convection in a Float Zone

Xiong

Shen

2021

Metals

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Two different analytic models, in which convection in the float zone is assumed, are developed to understand the solute redistributions during general seeding and quasi-seeding processes of TiAl alloys, respectively. The results suggest that the solute redistribution plays an important effect in the phase selection and microstructural development during the initial stage of seeding processes. In the initial stage of the quasi-seeding process, the interface concentration increases gradually and the solute diffusion boundary forms with the crystal growth of α phase. Correspondingly, a maximum constitutional undercooling with respect to β phase occurs ahead of the solidifying α interface and then decreases gradually. Simultaneously, the position where the maximum constitutional undercooling occurs also moves forward with regard to the interface. While in the initial stage of the general seeding process, the α phase can grow continuously as stable phase when the initial composition of the melt is higher than Al 48.9%. Under the influence of both the constitutional undercooling and Ti5Si3 particles, coarse dendrites form and then are transformed to cellular morphology. Nevertheless, the lamellar microstructure can still be aligned well during the entire seeding process. Besides, it is also found that the thickness of solute diffusion boundary decreases with the increase of convection intensity and thus, the growing interface become more stably correspondingly, which is beneficial to the lamellar alignment of TiAl alloys.

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Section: Solute Redistribution In the Steady Statementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Solute Redistribution on Seeding Process of TiAl Alloys with Limited Convection in a Float Zone

Xiong

Shen

2021

Metals

Self Cite

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“…Nonetheless, with a longer contact time, the surface quality and microstructure of TiAl alloys are still difficult to effectively control. Some methods that do not include a container, such as optical and induction floating zone furnaces9434445 and the electromagnetic confinement method, are also used for fundamental directional solidification studies of TiAl alloys2246. From the perspective of cost, using oxide ceramic crucible/mould remains the best choice for preparing castings of TiAl alloys by.…”

mentioning

confidence: 99%

Microstructure formation and interface characteristics of directionally solidified TiAl-Si alloys in alumina crucibles with a new Y2O3 skull-aided technology

Fan

Liu

et al. 2017

Sci Rep

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The microstructure evolution and interface characteristics of a directionally solidified Ti-43Al-3Si (at.%) alloy in an alumina (Al2O3) crucible with new Y2O3 skull-aided technology were investigated. The Y2O3-skull that is in contact with the TiAl-melt is relatively stable, which results in a more controlled reaction between the skull and the melt than in the case of an Al2O3 crucible is used. A thin reaction layer was formed between the mould and the melt through mutual diffusion. The layer thickness increased with increasing reaction time. The thickness of this layer was less than 80 μm for reaction times up to 5800 s. Y2O3 particles were not found in the specimen because the mould coating was prepared with fine Y2O3 powder without a binder, which prevented the Y2O3 particles splitting from the coating as a consequence of thermal physical erosion. The oxygen content of the TiAl-alloy increased with increasing reaction time. The total oxygen content of the solidified specimen was less than that of the specimen solidified in the Al2O3 crucibles. This new Y2O3 skull-aided technology is expected to improve the surface quality of TiAl-alloys and reduce the reaction between the crucible/mould and molten TiAl alloys during directional solidification processing with longer contact times.

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Quasi-Seeding Mechanism in Lamellae Alignment of TiAl Alloys During Directional Solidification

Shen

Xiong

et al. 2019

Metall Mater Trans A

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Stability of lamellar microstructures in a Ti–48Al–2Nb–2Cr alloy during heat treatment and its application to lamellae alignment as a quasi-seed

Cited by 16 publications

References 22 publications

Effect of Solute Redistribution on Seeding Process of TiAl Alloys with Limited Convection in a Float Zone

Effect of Solute Redistribution on Seeding Process of TiAl Alloys with Limited Convection in a Float Zone

Microstructure formation and interface characteristics of directionally solidified TiAl-Si alloys in alumina crucibles with a new Y2O3 skull-aided technology

Quasi-Seeding Mechanism in Lamellae Alignment of TiAl Alloys During Directional Solidification

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