työkarkaistumisen

Työkarkaistuminen, often translated as "work hardening" or "strain hardening" in English, is a metallurgical phenomenon where a metal becomes stronger and harder when it is plastically deformed. This process involves the movement and multiplication of dislocations, which are line defects in the crystal structure of the metal. As deformation increases, the density of these dislocations rises. These dislocations then impede each other's movement, making it more difficult for further plastic deformation to occur.

The effect of työkarkaistuminen is observed in many common metals, such as copper, aluminum, and iron. It is a key factor in manufacturing processes like rolling, drawing, and forging, where metals are shaped into desired forms. These processes inherently involve plastic deformation, leading to the work hardening of the material. The increased strength and hardness resulting from työkarkaistuminen can be beneficial, as it improves the mechanical properties of the metal for its intended application.

However, työkarkaistuminen also leads to a decrease in ductility, meaning the metal becomes more brittle and less able to deform without fracturing. This trade-off between strength and ductility is an important consideration in material selection and design. If a component requires both high strength and significant ductility, annealing, a heat treatment process, can be used to reverse the effects of työkarkaistuminen by reducing dislocation density.