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Deformation-induced γ → DI-α2 phase transformation occurring in the twin-intersection region of TiAl alloys

Published online by Cambridge University Press:  31 January 2011

C.L. Chen ,
W. Lu ,
L.L. He  and
H.Q. Ye
C.L. Chen
Affiliation:
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China; and Graduate School of Chinese Academy of Sciences, Beijing 100039, People’s Republic of China
W. Lu
Affiliation:
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China; and Graduate School of Chinese Academy of Sciences, Beijing 100039, People’s Republic of China
L.L. He*
Affiliation:
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China
H.Q. Ye
Affiliation:
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China
*
a)Address all correspondence to this author. e-mail: llhe@imr.ac.cn
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Abstract

Deformation-induced γ → DI-α2 phase transformation was verified to occur in the twin-intersection region of a Ti–45Al–8Nb (at.%) alloy compressed at room temperature. High-resolution image observations of the deformation-induced DI-α2 phase suggested that the orientation relationship between the DI-α2 and γ phases remained the typical one: (0001)DI−α2//{111}γ, [11¯20]DI−α2//〈101]γ. The conversion of stacking sequence from ordered face-centered tetragonal to ordered nonequilibrium hexagonal close-packed structure was accomplished by the movement of a/6〈11¯2] Shockley partial dislocations on every other {111}γ plane. Compositional analysis based on energy dispersive spectra revealed that the DI-α2 phase had the same composition as the matrix γ phase. No compositional diffusion occurred because the plastic deformation was carried out at room temperature. The strong stress concentration in the intersection region was the major force to induce the γ → DI-α2 phase transformation in the process of room-temperature compression.

Keywords

Phase transformationMicrostructureTransmission electron microscopy
Type
Articles
Information
Journal of Materials Research , Volume 22 , Issue 9 , September 2007 , pp. 2416 - 2422
Copyright
Copyright © Materials Research Society 2007

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