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The Influence of Boron Additions in Cast Ti-47AL-2Cr-2Nb-0.8B

Published online by Cambridge University Press:  22 February 2011

Daniel S. Schwartz  and
Donald S. Shih
Daniel S. Schwartz
Affiliation:
McDonnell Douglas Corporation, P.O. Box 516, St. Louis, MO 63166–0516
Donald S. Shih
Affiliation:
McDonnell Douglas Corporation, P.O. Box 516, St. Louis, MO 63166–0516
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Abstract

Morphology, fine structure, and chemistry of phases formed in cast Ti-47Al-2Cr-2Nb-0.8B due to boron addition were examined in detail. Boron acts an inoculant, refining and stabilizing the cast grain size. A curving ribbon-shaped phase was present throughout the material, related to the ordered phase Ti2AlCr. The ribbon phase had the B2 structure, with a0∼0.318nm. Many ribbons had a low degree of order, i. e. the material was a BCC mixture of Ti, Al, Nb, and Cr. Ribbon phase composition was variable, measured to be: Ti-(20–30)Al-(2–4)Nb-(5–16)Cr. TiB2 was present in small amounts, always in intimate contact with the ribbon phase. A (100)ribbon ‖ {1100}TiB2, (011)ribbon ‖ {1122}TiB2 orientation relationship was observed. It is proposed that the ribbon phase is a remnant of the high-temperature titanium aluminide β-phase, stabilized by dissolved boron.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 364: Symposium L – High-Temperature Ordered Intermetallic Alloys–VI , 1994 , 787
Copyright
Copyright © Materials Research Society 1995

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