MEASUREMENT OF THE COMPRESSIVE CREEP STRAIN RATES OF THE INDIVIDUAL PHASES WITHIN A LAMELLAR MICROSTRUCTURE

A fiducial line technique has been developed to determine the creep pr operties of the constitutent phases within a lamellar composite subjec t to compression creep deformation. The technique can yield informatio n on the total strain, creep rate, and the stress exponent and activat ion energy for creep of the individual phases within a lamellar micros tructure. The contribution of interphase interfacial sliding to the st rain of lamellar composites can also be evaluated by using the fiducia l line technique. Application of the fiducial line analysis to a two-p hase TiAl/Ti3Al lamellar alloy deformed in compression at 1080K and 38 0 MPa yields good agreement between the creep strain determined using the fiducial line analysis and the value directly measured from the cr ept specimen. The fiducial line analysis reveals that the TiAl phase w ithin the two-phase TiAl/Ti3Al lamellar microstructure creeps 2.2 time s faster than the Ti3Al phase and that interfacial sliding does not co ntribute to creep deformation of this alloy, within the resolution lim it of the fiducial line experiment.