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May 31, 2022 to June 3, 2022
Arabella Brauneck Hotel
Europe/Berlin timezone

Microstructure and texture evolution for high-temperature α phase in extruded β-containing TiAl alloy

Jun 3, 2022, 9:20 AM
Arabella Brauneck Hotel

Arabella Brauneck Hotel

Münchner Str. 25 83661 Lenggries
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Dr Yudong Zhang (LEM3 UMR 7239 CNRS, Université de Lorraine)


Increasing demands on modern turbines require (α2+γ) lamellar-structured TiAl alloys with fine colony size and properly aligned lamellae. As the lamellar structure is formed by the α→α2+γ phase transformation obeying Blackburn OR, the characteristics of lamellar structure depends directly on the high-temperature α phase. Thus, the lamellar structure optimization could be realized by the modification of high-temperature α phase through thermomechanical processing. In this work, the microstructure and texture evolution of high-temperature α phase in TNM alloy during hot extrusion at (α+β) phase field was investigated by high energy X-ray diffraction (HEXRD) and SEM electron back scatter diffraction (SEM-EBSD). Results show that with a small extrusion ratio (E2.25), the microstructure exhibits uniform and equiaxed α grains with a weak 〈112 ̅0〉//ED fiber texture. With the increase of extrusion ratio, the microstructure tends to exhibit bimodal structure (E7.11) consisting of deformed grains, fine primary DRXed grains with 〈101 ̅0〉//ED, as well as coarse grown grains with 〈112 ̅0〉//ED. The microstructure and texture evolution are resulted from a combination of extrusion parameter and the GB β phase. The increasing extrusion ratio, on one hand, increases the deformation degree and the extrusion rate, so that the considerable stored energy cannot be released in a short time. On the other hand, the large extrusion ratio elongates the GB β phase leading to more α/β interfaces which served as pining points inhibited the low-angle boundaries to evolve into high-angle boundaries. Both of them keep more deformed α grains orientated with 〈101 ̅0〉//ED retained in the sample with high extrusion ratio. Accordingly, a preferred grain growth happened to the <11-20>-orientated grains due to the high interface energy.
Keywords: TiAl alloy, extrusion, texture, high energy X-ray diffraction (HEXRD), SEM-EBSD

Primary author

Dr Yudong Zhang (LEM3 UMR 7239 CNRS, Université de Lorraine)


Dr Fengming Qiang (University of Lorraine) Prof. Hongchao Kou (Northwestern Polytechnical University, China) Prof. Jinshan Li (Northwestern Polytechnical University, China ) Prof. Emmanuel Bouzy (University of Lorraine, France)

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