High temperature creep of dispersion-strengthened Al-1.5 vol%Be alloy has been studied over a stress range 3.1 × 10-5~5.9 × l0-4E (E: the Young's modulus of Al matrix), which corresponds to 0.40~5.lσor (σor: the Orowan stress), at temperatures from 473 to 723 K. It is found that there occurs a threshold stress for creep deformation, σth, and the value of σth is approximately equal to that of σor and their ratio, σth/σor, is almost independent of the particle size and test temperature. At stresses below σth, plastic deformation of very slow rates takes place which may be associated with grain-boundary sliding and diffusional creep. In-situ HVEM observation reveals that the interaction between dislocation and particles is of attractive type and no dislocation line is visible at the particle/matrix interface, indicating that the stress field of a dislocation is almost completely relaxed at the interface. The observed threshold stress is discussed from the viewpoint of the attractive interaction.
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