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 properties of the constitutent phases within a lamellar composite subject to compression creep deformation. The technique can yield information on the total strain, creep rate, and the stress exponent and activation energy for creep of the individual phases within a lamellar microstructure. The contribution of interphase interfacial sliding to the strain of lamellar composites can also be evaluated by using the fiducial line technique. Application of the fiducial line analysis to a two-phase TiAl/Ti3Al lamellar alloy deformed in compression at 1080K and 380 MPa yields good agreement between the creep strain determined using the fiducial line analysis and the value directly measured from the crept specimen. The fiducial line analysis reveals that the TiAl phase within the two-phase TiAl/Ti3Al lamellar microstructure creeps 2.2 times faster than the Ti3Al phase and that interfacial sliding does not contribute to creep deformation of this alloy, within the resolution limit of the fiducial line experiment.