brittleness

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Stress-strain diagram : brittle failure in red, deformation failure in gray

The brittleness indicates the extent to which a material can be elastically deformed before it breaks . In contrast to brittleness, toughness or ductility describes the behavior in the event of plastic deformation.

These material properties can be determined in the tensile test :

• Brittle materials tear close to the elastic limit with no or only little plastic deformation ( brittle fracture ). Such materials are usually very hard : diamond , carbides , nitrides , salts , ceramics and glass but z. B. also gray cast iron and bakelite .
• In contrast, ductile materials - including many metals and plastics - can be plastically deformed to a comparatively large extent before they break as a result of the deformation ( deformation fracture ).

Most materials become brittle as the temperature drops . Face-centered cubic metals or austenitic steels are an exception .

The fracture mechanics of brittle materials applies to brittle metals .

Embrittlement

Various factors can cause a material to become more brittle than when it was new, due to the process of embrittlement .

• Plastics can become brittle if the plasticizer escapes from them. The escape is promoted by environmental factors such as high temperatures or strong sunlight (" UV "). This happens more quickly when the vapor pressure of the plasticizer increases.
• Disturbances in the crystal lattice: under the influence of ionizing radiation, iron and steel become brittle . Iron atoms are pushed from their lattice sites by neutrons , causing a cascade of collisions that form clusters of defects in the lattice .
• Storage of hydrogen in some types of steel leads to hydrogen embrittlement , which in turn is based on lattice defects.

See also

Wiktionary: brittleness  - explanations of meanings, word origins, synonyms, translations

Individual evidence

1. ↑ Reactors under constant fire. In: FAZ , September 22, 2010