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Gamma-Titanium Aluminide Reinforced with A12O3 and TiB2 Fibers*

Published online by Cambridge University Press:  01 January 1992

Darrell Dixon  and
Joseph W. Newkirk
Darrell Dixon
Affiliation:
The Bionetics Corporation, Arnold Air Force Base, TN 37389-3400
Joseph W. Newkirk
Affiliation:
University of Missouri-Rolla, Metallurgical Engineering Department, Rolla, MO 65401
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Abstract

A two-phase Ti-47Al-2Ta composite reinforced with a titanium diboride (TiB2) and two alumina fibers was processed by hot isotatic pressing and heat treated to simulate service conditions. Diffusion couples were heat treated between 593°C and 982°C for up to 500 h and analyzed using a scanning electron microscope and energy dispersive x-ray spectroscopy.

The fibers used were 3M® alumina, Sapphikon® sapphire, and Textron Specialty Materials TiB2. Observations reveal reaction layers, cracking fibers due to thermal stress, and chemical interactions between ternary addition of Ta with the fibers. Alumina is thermodynamically stable in TiAl, and its coefficient of thermal expansion closely matches TiAl. Observations revealing alumina as a good potential reinforcement in TiAl are discussed. Thermodynamic information supports TiB2 stability in two-phase TiAl. A three-fold increase of Ta at the fiber/ matrix interface of TiB2 is evidence of a lack of homogeneity due to Ta mobility. This indicates a possible loss of oxidation resistance provided by the Ta addition.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 288: Symposium L – High-Temperature Ordered Intermetallic Alloys V , 1992 , 1063
Copyright
Copyright © Materials Research Society 1995

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References

REFERENCES

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