Failure Mechanisms

· Both Coble and Nabarro-Herring creep involve a change in the shape of the grains of the polycrystalline material.
· In Coble creep, diffusion along grain boundaries and surfaces controls the creep rate. This process has a lower diffusion energy than bulk diffusion.

After: Courtney, "Mechanical Behavior of Materials," McGraw Hill (1990)
· The diagram illustrates the matter flow associated with this creep process for an idealized grain boundary. A more realistic grain boundary configuration is also shown.