Creep of fully lamellar near {gamma}-TiAl intermetallics

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20001565

Beddoes, J; Zhao, L; Chen, W R; Du, X

The influence of the fully lamellar morphology and third phase {beta} on the creep properties of near {gamma}-TiAl intermetallics is presented. Specifically, the effect of improved microstructural control obtainable by a stepped cool, involving furnace cooling and air cooling from the {alpha} single phase, on creep resistance is demonstrated for three near {gamma}-TiAl intermetallics: binary Ti-48Al, ternary Ti-48Al-2W and Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si. The results indicate that appropriate stepped cooling can be used to reduce the lamellar interface spacing without the formation of Widmanstaetten, feathery {gamma} or {gamma}{sub M} structures, leading to longer creep life and reduced creep strain rates. A second benefit of stepped cooling is prevention of {beta} formation during cooling from the {alpha} phase, allowing controlled {beta} precipitation during aging at 950 C. Creep tests on variously aged Ti-48Al-2W indicate that {beta} precipitation along lamellar grain boundaries improves creep resistance. Development of a uniform fully lamellar structure in Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si significantly improves creep resistance. Applying the stepped cool to this alloy allows the precipitation of {beta} and silicides to be controlled during lower temperature aging.

• Research Organization: Carleton Univ., Ottawa, Ontario (CA)
• Sponsoring Organization: Natural Sciences and Engineering Research Council; Department of National Defence (Canada)
• OSTI ID: 20001565
• Report Number(s): CONF-981104--; ISBN 1-55899-458-0; ISSN 1067-9995
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CREEP
EXPERIMENTAL DATA
HEAT TREATMENTS
INTERMETALLIC COMPOUNDS
LAMELLAE
MANGANESE ALLOYS
MICROSTRUCTURE
MOLYBDENUM ADDITIONS
NIOBIUM ALLOYS
SILICON ADDITIONS
TITANIUM ALLOYS
TUNGSTEN ALLOYS