Abstract

A theory describing the high-temperature creep of polycrystalline graphite is developed. Equations are derived which describe the creep of graphite produced by the climb of edge dislocations distributed near the tips of basal plane cracks. These dislocations are characterized as follows: (i) their Burgers vectors are parallel to the c-axis, and (ii) they force the crack faces apart. The theory predicts and experimental results agree with the following: (1) cracks are observed microscopically; (2) the creep strain in the early stage of creep is proportional to the square root of time; (3) the creep strain at a given moment in time is proportional to the third power of stress; (4) the creep rate at a given creep strain is proportional to the 6th power of the stress; (5) the apparent activation energy of creep is appreciably larger than the self-diffusion activation energy and the creep recovery activation energy; and (6) extensive recovery creep based on reverse dislocation climb is predicted and observed.

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