Diffusional Creep Mechanisms

Creep extension without dislocation movement across grains may be obtained in polycrystalline aggregates by diffusion through the grains (Nabarro-Herring) or through grain boundaries (Coble). These mechanisms are compared with a suggestion that creep can occur by grain-boundary sliding controlled by diffusion which can lead to movement along the boundary of grain-boundary protrusions and can be accommodated by diffusion around triple points.