Influence of Step Aging on Creep Behavior and Microstructural Evolution of Fine-Grained Fully Lamellar XD TiAl Alloys

Fine-grained fully lamellar (FGFL) structures of XD TiAl alloys (Ti-45 and 47Al-2Nb-2Mn+0.8vol.%TiB2) (at.%) were stabilized to varying degrees by different aging treatments. Specimens with and without aging were creep tested at 760°C and 207 MPa. It was found that during creep deformation, degradation of the lamellar structure involving coarsening within the colonies and spheroidization at colony boundaries occurred, forming fine globular structures at the colony boundaries and increasing the creep rate. Aging treatments stabilized the lamellar structure and retarded the coarsening and spheroidization processes during creep deformation. As a result, the aged specimens exhibited lower minimum creep rates and longer creep lives than the unaged specimens. A multiple step aging stabilized the lamellar structure to the greatest extent and suppressed other degradation processes during aging, resulting in the best creep resistance. These results demonstrate that the multiple step aging is the optimal aging condition for stabilizing FGFL XD TiAl alloys.

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Effect of microstructural stability on creep behavior of 47XD TiAl alloys with fine-grained fully lamellar structure

Scripta Materialia ◽

10.1016/j.scriptamat.2004.08.027 ◽

2005 ◽

Vol 52 (1) ◽

pp. 45-50 ◽

Cited By ~ 30

Author(s):

Hanliang Zhu ◽

D.Y. Seo ◽

K. Maruyama ◽

P. Au

Keyword(s):

Creep Behavior ◽

Lamellar Structure ◽

Microstructural Stability ◽

Tial Alloys ◽

Fine Grained ◽

Fully Lamellar

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Microstructural stability of fine-grained fully lamellar XD TiAl alloys by step aging

Metallurgical and Materials Transactions A ◽

10.1007/s11661-005-0225-x ◽

2005 ◽

Vol 36 (5) ◽

pp. 1339-1351 ◽

Cited By ~ 22

Author(s):

Hanliang Zhu ◽

K. Maruyama ◽

D. Y. Seo ◽

P. Au

Keyword(s):

Microstructural Stability ◽

Tial Alloys ◽

Fine Grained ◽

Fully Lamellar

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Effect of Heat Treatment on Microstructure and Mechanical Property of 45XD and 47XD TiAl Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.581 ◽

2005 ◽

Vol 475-479 ◽

pp. 581-584 ◽

Cited By ~ 3

Author(s):

H. Zhu ◽

Dong Yi Seo ◽

Kouichi Maruyama

Keyword(s):

Heat Treatment ◽

Mechanical Property ◽

Lamellar Structure ◽

Tial Alloys ◽

Fine Grained ◽

Break Up ◽

Fully Lamellar ◽

Hardness Values ◽

Microstructure And Mechanical Property ◽

Microstructural Examination

The effect of heat treatment on microstructure and property of Ti-45 and 47Al-2Nb-2Mn+0.8%vol.%TiB2 alloys (45XD and 47XD) has been studied. Annealing and subsequent oil quench produced fine-grained fully lamellar structure (FGFL) in both alloys. For microstructural stabilization, the FGFL structures were subjected to different aging treatments. Microstructural examination showed that degradation of the FGFL structure, such as coarsening of γ lamellae, recrystallization of γ grains and break-up of a2 lamellae, presented to varying degrees after different aging treatments. Hardness values in the aged alloys decreased due to the degradation. The creep resistances were improved in the aged alloys though the degradation occurred, indicating that the aging treatments stabilized the FGFL structures effectively. The differences in the changes of properties caused by different aging treatments and compositions were compared in combination with the microstructural variants.

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