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Vol.35, No.9, 1130 ~ 1137, 1997

Title

Microscopic Observation of Superplastic Deformation in a Ti3Al-Nb Two-Phase Alloy

김진홍 , 박찬경 , 장영원 Jin Hong Kim , Chan Gyung Park , Tae Kwon Ha , Young Won Chang

Abstract

Microscopic aspects of superplastic deformation behavior in an α₂+β_0 Ti₃Al-Nb alloy have been studied by using transmission electron microscopy. Ti-24A1-11Nb specimen with grain size of 3.6㎛ was superplastically deformed at 970℃ and at an initial strain rate of 10^(-3)/sec. Localized dislocation activities along α₂/β_0 phase boundaries and α₂/α₂ grain boundaries with almost no dislocations inside the a₂ grains were observed in the superplastically deformed specimen. This result shows that phase boundary sliding (PBS) and grain boundary sliding (GBS) played a major role in superplastic deformation of this alloy. Severe deformation of soft β_0 phase and dislocation pile-ups inside the α₂ grains at/toward triple-points were also observed. From these results, it is concluded that the local stress concentration produced by PBS and GBS is accommodated by dislocation motion inside β_0 and α₂ phases.

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