Permanent shape change driven by stress-biased atomic or vacancy diffusion. Different chemical potentials at differently stressed grain surfaces drive material transfer, requiring grain-shape accommodation. Bulk and boundary transport give different grain-size dependencies.
Diffusional material creep dominated by grain-boundary transport. An ideal scaling is . Its stronger grain-size dependence and typically lower transport activation energy distinguish it from bulk-diffusion material creep.
Diffusional material creep dominated by transport through grain interiors. For an equiaxed-grain model, , with geometric factor , atomic volume and grain size . It is linear in stress in this ideal limit.
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Diffusion creep is a mechanism of deformation that occurs in materials, particularly in solids under high temperature and stress conditions. It is characterized by the movement of atoms or vacancies within the crystal lattice of a material, allowing it to deform without the need for dislocation movement, which is a more conventional mechanism of plastic deformation. The process occurs through the diffusion of atoms in the lattice, which can happen via two main types: grain boundary diffusion and lattice diffusion.