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RESEARCH PAPERS

Stress Versus Temperature Dependence of Activation Energies for Creep

[+] Author and Article Information
A. D. Freed, S. V. Raj

National Aeronautics and Space Administration, Lewis Research Center, Cleveland, Ohio

K. P. Walker

Engineering Science Software, Inc., Smithfield, RI

J. Eng. Mater. Technol 114(1), 46-50 (Jan 01, 1992) (5 pages) doi:10.1115/1.2904139 History: Received October 01, 1990; Revised April 11, 1991; Online April 29, 2008

Abstract

The activation energy for creep at low stresses and elevated temperatures is associated with lattice diffusion, where the rate controlling mechanism for deformation is dislocation climb. At higher stresses and intermediate temperatures, the rate controlling mechanism changes from dislocation climb to obstacle-controlled dislocation glide. Along with this change in deformation mechanism occurs a change in the activation energy. When the rate controlling mechanism for deformation is obstacle-controlled dislocation glide, it is shown that a temperature-dependent Gibbs free energy does better than a stress-dependent Gibbs free energy in correlating steady-state creep data for both copper and LiF-22mol percent CaF2 hypereutectic salt.

Copyright © 1992 by The American Society of Mechanical Engineers
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