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Evolution of Antiphase Domains and γ Lamellae in Ti-39at%Al Single Crystals

Published online by Cambridge University Press:  26 February 2011

Yuichiro Koizumi
Affiliation:
koizumi@ams.eng.osaka-u.ac.jp, Osaka University, Adaptive Machine Systems, 2-1, Yamadaoka, Suita, 565-0871, Japan, 81-6-6879-7434, 81-6-6879-4174
Kazuki Iwamoto
Affiliation:
loudness_random8186@yahoo.co.jp, Osaka University, Adaptive Machine Systems, 2-1, Yamadaoka, Suita, 565-0871, Japan
Takayuki Tanaka
Affiliation:
takayuki.tanaka@ams.eng.osaka-u.ac.jp, Osaka University, Adaptive Machine Systems, 2-1, Yamadaoka, Suita, 565-0871, Japan
Yoritoshi Minamino
Affiliation:
minamino@ams.eng.osaka-u.ac.jp, Osaka University, Adaptive Machine Systems, 2-1, Yamadaoka, Suita, 565-0871, Japan
Nobuhiro Tsuji
Affiliation:
tsuji@ams.eng.osaka-u.ac.jp, Osaka University, Adaptive Machine Systems, 2-1, Yamadaoka, Suita, 565-0871, Japan
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Abstract

We studied antiphase domain (APD) growth and lamellar structure formation during isothermal annealing of Ti-39at%Al single crystals at α2+γ dual phase temperature after quenching from α single phase state, intending to obtain a APD/lamellae mixed microstructure and to examine whether such a microstructure provides a strength higher than that obtained only by refining lamellar structure. The effect of plastic deformation prior to the annealing was also examined expecting a acceleration of γ lamellae formation through a preferential nucleation of γ-plates at dislocations. The lower was the annealing temperature, the smaller both the APD size and the lamellar spacing at the moment of a homogeneous lamellar structure formation tended to be, although naturally both the APD growth and the γ lamellae formation were slower. However, the APD size in the homogeneous lamellar structure was no smaller than 400 nm. A structure with finer APDs and finer lamellar structure was obtained by deforming the crystal before annealing since the lamellar structure formation was accelerated and the time for APD growth before the lamellar structure formation was shortened. For instance, a structure with an average lamellar spacing of 88 nm and an average APD size of 214 nm was obtained by deforming the crystals to 10 % plastic strain and subsequently annealing at 1073 K for 1×104 s, while no γ plate was obtained only by such an annealing without deformation.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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