Creep behavior of a fully transformed near [gamma]-TiAl alloy Ti-48Al-2Cr

Journal Article · Sun Jan 01 00:00:00 EST 1995 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(95)90270-8· OSTI ID:6823388

Es-Souni, M; Wagner, R ^[1]; Bartels, A ^[2]

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1. GKSS-Research Centre, Geesthacht (Germany). Inst. for Materials Research
2. Technical Univ. Hamburg-Harburg, Hamburg (Germany)

The creep deformation behavior and creep microstructures of a dual phase TiAl/Ti[sub 3]Al alloy, Ti-48Al-2Cr (at.%) with a fully transformed lamellar structure, have been investigated at 800 C in tension creep. The creep curves show no steady state creep rate, rather a minimum creep rate was obtained followed by a steep increase in the creep rate. The application of a power-law creep equation of the type [dot [epsilon]] = A[sigma][sup n] leads to a stress exponent n = 7.6. The deformation microstructures show no deformation twins and essentially consist of [1/2]<110> dislocations; recovered structures were observed in the fine [gamma]-grains at colony boundaries whereas long and curved [1/2]<110> segments were found in the [gamma]-lamellae. These microstructural observations suggest a dislocation controlled creep; it ensues that the stress exponent obtained using power-law creep does not reflect the operating creep mechanism. This is attributed to early nucleation and growth of voids and cavities at colony boundaries which do not allow steady-state creep to be established, an underlying condition for the applicability of the power-law equation above. The nucleation and growth of void and cavities are thought to arise as a result of stress buildup at colony boundaries which in turn results from the dependence of deformation behavior on the orientation of the lamellar colonies with respect to the tensile axis. The loss of creep strength is found to be primarily due to growth and coalescence of these voids and cavities.

• OSTI ID: 6823388
• Journal Information: Acta Metallurgica et Materialia; (United States), Vol. 43:1; ISSN 0956-7151
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CREEP
MICROSTRUCTURE
CHROMIUM ALLOYS
TITANIUM BASE ALLOYS
DISLOCATIONS
INTERMETALLIC COMPOUNDS
MATHEMATICAL MODELS
METALLURGICAL EFFECTS
VOIDS
ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
LINE DEFECTS
MECHANICAL PROPERTIES
TITANIUM ALLOYS
360102* - Metals &amp; Alloys- Structure &amp; Phase Studies
360103 - Metals &amp; Alloys- Mechanical Properties