Cleavage
Definition
Fracture by separation along specific crystallographic planes, typically {100} planes in body-centred-cubic metals. The fracture surface is flat at the grain scale and produces characteristic river marks and fan patterns.
- Fracture mode
- Transgranular, along crystallographic planes
- Typical planes
- {100} in BCC metals
- Macroscopic look
- Flat, faceted grain surfaces
- Microscopic markers
- River marks, fan patterns
Common questions
How does cleavage fracture differ from ductile fracture in a failure examination?+
Cleavage fractures show flat, crystallographically controlled facets with river marks radiating from the origin and little visible plastic deformation, whereas ductile fracture produces dimpled surfaces from microvoid coalescence and visible necking.
What do river marks on a cleavage surface tell an examiner?+
River marks form as the crack front crosses grain boundaries and step height changes, and their branching direction points back toward the fracture origin, which is useful for locating the failure initiation site.
Related terms
- Brittle Fracture
- Fracture with little or no plastic deformation, occurring by rapid cleavage through grains or along grain boundaries. The surface is flat, often...
- Cup-and-Cone Fracture
- The classic macroscopic appearance of ductile tensile fracture in round bar: a flat central zone (the cup) formed by void coalescence surrounded...
- Ductile Fracture
- Fracture preceded by extensive plastic deformation, in which microvoids nucleate at inclusions, grow, and coalesce to form the fracture surface. The surface...
- Intergranular Fracture
- Fracture path running along grain boundaries rather than through grains. Indicates boundary weakness from segregation, embrittlement, or environmental attack, and produces a...
- SEM Fractography
- The use of scanning electron microscopy to image fracture surfaces at magnifications beyond the optical limit, revealing dimple size and distribution in...