ABSTRACT
Atomic motion in dispersion-strengthened alloys, as well as other materials, is of major importance when elevated-temperature properties are of concern. For example, (1) prolonged resistance to environmental attack can be related to the rate at which diffusion brings alloying elements to the surface for the formation of oxidation/corrosion-resistant scales and (2) elevated-temperature mechanical properties are normally thermally activated processes often related to the diffusivity of particular species. Although these two examples both involve diffusioncontrolled behavior, the obvious driving force is different for each: the former is due to composition gradients, while the latter is the result of the applied stress. In actuality, the cause of atomic motion in all cases is differences in chemical potentials; thus study and understanding of diffusion phenomena under one driving force (i.e., composition gradients) can lead to expectations and conclusions when other forces (stress and temperature gradients for example) are active.
