Intergranular fracture
An intergranular fracture is a fracture that follows the grains of the material, where cracks that take place along the grain boundary. In a wall of bricks it would correspond to a fracture that takes place in the mortar that keep together bricks. In metals with multiple lattice organizations, when one lattice ends and another begins, the fracture changes direction to follow the new grain. This results in a fairly jagged looking fracture with straight edges of the grain and shiny surface may be seen.
In ceramics, interganular fractures propagate through grain boundaries, producing smooth bumpy surfaces where grains can be easily identified.
There are several processes that can lead to intergranular fracture.
- Microvoid nucleation and coalescence at inclusions or second phase particles located along grain boundaries
- Grain boundary crack and cavity formation associated with elevated temperature stress rupture condition.
- Decohesion between contiguous grain due to presence of impurity at grain boundaries and in the presence of hydrogen and liquid metals.
- Stress corrosion cracking associated with chemical dissolution along grain boundaries.
- Cyclic loading when the material insufficient number of independent slip systems to accommodate plastic deformation between contiguous grain leading to grain boundaries.
Think of several wooden jigsaw puzzle pieces with the grains showing, but with each piece having grains running in a different direction.An intergranular fracture follows the edges of the puzzle pieces, ignoring the grains in the wood.
This is opposed to a Transgranular fracture.