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Abstract
Biaxial creep tests were performed on fine-grained Ti–3Al–2.5V tubing at 823 and 873 K in the stress range σ/E = 1.7 × 10−4 to σ/E = 5.9 × 10−4. Subsequently, the creep data were analysed to determine the stress exponent and activation energy. A stress exponent value of 1 and an activation energy equal to that for grain boundary diffusion were suggestive of a Coble creep-controlled deformation regime. However, discrepancy between the experimental creep rates and Coble creep model predictions along with subsequent observation of deformed microstructures decorated with slip bands implied the operation of a different viscous creep mechanism. A slip band model proposed by Spingarn and Nix was found to provide a better description of the experimental strain rates rather than the conventional viscous creep mechanisms. High-resolution transmission electron microscopy studies confirmed the nature of these bands.
Acknowledgements
We gratefully acknowledge the grant # DMR-0412583 from the US National Science Foundation for supporting this work. The help extended by S. Johansson and G. Ramos in sample preparation is acknowledged.