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Effect of Initial Microstructure on the Compatibility of Rapidly Solidified Ti-Rich TiAl Powder

Published online by Cambridge University Press:  15 February 2011

M. Nishida ,
A. Chiba ,
Y. Morizono ,
T. Kai  and
J. Sugimoto
M. Nishida
Affiliation:
Department of Materials Science, Kumamoto University, Kurokami, Kumamoto 860, Japan, nishida@gpo.kumamoto-u.ac.jp
A. Chiba
Affiliation:
Department of Materials Science, Kumamoto University, Kurokami, Kumamoto 860, Japan, nishida@gpo.kumamoto-u.ac.jp
Y. Morizono
Affiliation:
Department of Materials Science, Kumamoto University, Kurokami, Kumamoto 860, Japan, nishida@gpo.kumamoto-u.ac.jp
T. Kai
Affiliation:
Graduate Student, Kumamoto University, Kurokami, Kumamoto 860, Japan
J. Sugimoto
Affiliation:
Department of Materials Science, Kumamoto University, Kurokami, Kumamoto 860, Japan, nishida@gpo.kumamoto-u.ac.jp
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Abstract

Initial microstructure dependence of compactibility at elevated temperature in rapidly solidified Ti-rich TiAl alloy powders produced by plasma rotating electrode process (PREP) has been investigated. There were two kinds of powders with respect to the microstructure. The first one had a surface relief of a martensitic phase, which was referred as M powder. The second one had a dendritic structure, which was referred as D powder. α2+γ microduplex and α2/γ lamellar structures were formed in Mand D powders of the Ti-40 at%Al alloy by heat treatment at 1273 K, respectively. The microduplex structure consisted of γ precipitate in the twin related α2 matrix with the usual orientation relationship. It was difficult to compact the D powder by hot pressing at 1273 K under 50 MPa for 14.4 ks. On the other hand, the M powder was compacted easily by hot pressing with the same condition. The twin related α2 and α2 boundary changed to random ones and the α2 and γ phases were lost the usual orientation relationship in the duplex structure during the hot pressing. In other words, the low energy boundaries were changed to the high energy ones suitable for grain boundary sliding. Dislocations were scarcely observed inside of both the α2 and γ crystal grains. It was concluded that the grain boundary sliding was a predominant deformation mode in the M powder during the hot pressing. D and M powders in Ti-45 and 47 at%Al alloys showed the same tendency as those in Ti-40 at%Al alloy during hot pressing.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 460: Symposium Z – High-Temperature Ordered Intermetallic Alloys VII , 1996 , 45
Copyright
Copyright © Materials Research Society 1997

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References

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