arbejdstivning

Arbejdstivning is a Danish term that translates to "work hardening" or "strain hardening" in English. It refers to a phenomenon in metallurgy where a metal becomes stronger and harder when it is plastically deformed. This occurs because the deformation process introduces and multiplies dislocations within the crystal structure of the metal. Dislocations are line defects that allow atoms to move past each other, facilitating deformation. However, as their density increases, they begin to impede each other's movement, requiring more force to induce further plastic deformation.

This increase in strength and hardness comes at the expense of ductility, meaning the material becomes more brittle and less able to deform without fracturing. The extent of work hardening depends on the amount of plastic deformation the material undergoes. Cold working, which is deformation performed below the recrystallization temperature of the metal, is a common method used to deliberately induce work hardening. Processes such as rolling, drawing, and forging often result in work-hardened materials.

Work hardening is a crucial aspect of metal manufacturing. It allows engineers to tailor the mechanical properties of metals for specific applications. For example, metals used in structural components or tools often benefit from the increased strength provided by work hardening. However, if a material is work-hardened too much, it may become too brittle for its intended use. In such cases, annealing, a heat treatment process, can be used to soften the metal by allowing recrystallization and reducing the dislocation density, thereby restoring ductility.