Journal Article

PUBDB-2025-01024

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Stress-induced orthorhombic O phase in TiAl alloys

Liu, X. ; Song, L. (Corresponding author)Extern* ; Pyczak, F.Extern* ; Stark, A.Extern*Hereon* ; Wang, L. ; Guo, X.Extern* ; Zhang, T.

2025
Elsevier Science Amsterdam [u.a.]

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Please use a persistent id in citations: doi:10.1016/j.actamat.2025.120751  doi:10.3204/PUBDB-2025-01024

Abstract: The orthorhombic O phase precipitation within the D0$_{19}-\alpha_2$ phase has attracted increasing attention recently inhigh Nb containing TiAl (high Nb-TiAl) alloys since the precipitation temperature is close to the expected servicetemperature of the alloys. In this study, in-situ synchrotron high energy X-ray diffraction (HEXRD) reveals thatthe O phase precipitates at 550 ◦C while it dissolves into the $\alpha_2$ phase at 750 ◦C during heat treatments. However,under external stress the O phase unexpectedly precipitates from $\alpha_2$ phase at 800 ◦C and even 900 ◦C. The Ophase formation proceeds further in the presence of a critical stress promoted by internal stress accumulation inthe $\alpha_2$ phase, whereas the reverse O → $\alpha_2$ phase transformation takes place when the internal stresses are relaxed.Additionally, it has been revealed that the O phase preferentially precipitates from specifically oriented $\alpha_2$ grainswith one of their <11$\bar{2}$0> directions aligned perpendicular and their 〈0001〉directions rotated by an angle of 120◦ out of the external load axis. This $\alpha_2$ phase orientation facilitates the $\alpha_2$ → O crystal transition during uniaxialcompression. Transmission electron microscopy (TEM) study shows that stress-induced $\alpha_2$ → O transformation isgoverned by small atomic shifts in the $\alpha_2$ lattice. In addition, the selective growth of certain O variants viashuffling along an [11$\bar{2}$0]$\alpha_2$ direction is found to accommodate the external strain component in this direction.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)
2. Helmholtz-Zentrum Hereon (Hereon)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)

Experiment(s):

1. PETRA Beamline P07 (PETRA III)

Appears in the scientific report 2025

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Database coverage:
; ; Clarivate Analytics Master Journal List ; Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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