On the creep deformation of a cast near gamma TiAl alloy Ti-48Al-1Nb

Journal Article · Tue Sep 01 04:00:00 EDT 1992 · Acta Metallurgica; (United States)

OSTI ID:7000066

Hayes, R W ^[1]; London, B ^[2]

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1. Metals Technology, Inc., Northridge, CA (United States)
2. Howmet Corp., Whitehall, MI (United States)

In this paper, the steady-state creep deformation behavior of a cast two phase gamma TiAl alloy having the composition Ti--48Al--1b (at.%) is studied. Tension creep tests using the stress increment technique ([sigma][sub 1] [lt] [sigma][sub 2] [lt] [sigma][sub 3]) were conducted over the temperature range of 704--850[degrees]C at constant initial applied stress level of 103.4--241.3 MPa. The activation energy for creep over the temperature and stress regime of this study varied from 217.5 kJ/mol (137.8 MPa) up to 341.0 kJ/mol (206.8 MPa) with an average value of 326.4 kJ/mol. This is well within the range of values previously measured for gamma TiAl alloys where creep controlled by volume diffusion has been suggested as rate controlling. The stress exponents measured were 5.0 at 704[degrees]C, 4.9 at 750[degrees]C, 4.7 at 800[degrees]C and 4.46 at 850[degrees]C. Using the activation energy of 326.4 kJ/mol, the temperature compensated steady-state creep rate was plotted against log stress with all temperatures collapsing onto a single line having a slope equal to 4.95. Using conventional creep analysis, this value of the stress exponent can be taken as suggestive of dislocation climb controlled power law creep as the operative deformation mechanism within the stress and temperature regime of the present study. The boundary separating the lamellar grains in two phase gamma TiAl alloys having the duplex microstructure may be a very important aspect of this microstructure with respect to creep deformation resistance.

• OSTI ID: 7000066
• Journal Information: Acta Metallurgica; (United States), Journal Name: Acta Metallurgica; (United States) Vol. 40:9; ISSN 0001-6160; ISSN AMETAR
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ACTIVATION ENERGY
ALLOYS
ALUMINIUM ALLOYS
CREEP
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DEFORMATION
DISLOCATIONS
ENERGY
GRAIN SIZE
LAMELLAE
LINE DEFECTS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NIOBIUM ALLOYS
SIZE
STEADY-STATE CONDITIONS
STRAIN RATE
STRESSES
TITANIUM ALLOYS
VERY HIGH PRESSURE