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Effect of A12Ti Phase on Plastic Behavior in Ti-62.5at%Al Single Crystals

Published online by Cambridge University Press:  10 February 2011

Takayoshi Nakano ,
Koutarou Hayashi ,
Keishi Ashida  and
Yukichi Umakoshi
Takayoshi Nakano
Affiliation:
Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2–1, Yamada-oka, Suita, Osaka 565–0871, Japan
Koutarou Hayashi
Affiliation:
Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2–1, Yamada-oka, Suita, Osaka 565–0871, Japan
Keishi Ashida
Affiliation:
Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2–1, Yamada-oka, Suita, Osaka 565–0871, Japan
Yukichi Umakoshi
Affiliation:
Department of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2–1, Yamada-oka, Suita, Osaka 565–0871, Japan
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Abstract

The microstructure and plastic deformation behavior in Ti-62.5at.%Al single crystals were investigated focusing on effect of the formation of h- and r-AI2Ti precipitates. Crystal structure, morphology and volume fraction of the precipitates depended strongly on the annealing temperature. The r-A12Ti phase precipitated as a plate in the Li0 matrix containing A15Ti3 superstructure below 1200°C, while the h-Al2Ti phase appeared at the higher temperature. The r-A12Ti had six-fold periodicity along the c-axis of the L10 structure and formed a semi-coherent boundary with the matrix maintaining an orientation relationship with {101)r-A12Ti//{101)L10 In contrast, small particles of h-A12Ti with three-fold periodicity along the b-axis were homogeneously distributed in the matrix forming an obscure coherent phase boundary.

Yield stress for specimens with a [201] loading axis anomaly increased showing a maximum peak around 800°C and then rapidly decreased. [111] <110] slip was dominant in the Li0 matrix and research-article-Al2Ti precipitates at temperatures below the peak, while slip occurred on (001) above the peak temperature. The anomalous strengthening and the change in operative slip system were discussed focusing on the effect of anisotoropy of APB energy and formation of Al2Ti precipitates.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 552: Symposium KK – High-Temperature Ordered Intermetallic Alloys VIII , 1998 , KK5.9.1
Copyright
Copyright © Materials Research Society 1999

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References

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