Failure Mechanisms

· Grain boundary sliding is necessary for the prevention of void formation in the material:
* (a) A polycrystalline sample prior to creep with fiducial marks shown.

* (b) The effect of deforming by diffusional creep without any grain boundary sliding. Voids form at the grain boundaries.
* (c) Creep deformation accompanied by grain boundary sliding. No voids form.

From: Courtney, "Mechanical Behavior of Materials,"
McGraw Hill (1990)