työkovettumista

Työkovettumista, also known as work hardening or strain hardening, is a phenomenon observed in ductile metals where plastic deformation leads to an increase in strength and hardness. When a metal is subjected to stress beyond its elastic limit, permanent changes occur at the microscopic level. Dislocations, which are line defects in the crystal lattice of metals, move and interact during plastic deformation. As deformation progresses, these dislocations multiply and tangle with each other, impeding their further movement. This increased resistance to dislocation motion makes it harder for the metal to deform further, thus increasing its yield strength and tensile strength.

The process of work hardening is often utilized in manufacturing to improve the properties of metal components. For example, cold working processes like rolling, drawing, and forging induce work hardening. This makes the metal stronger and more resistant to wear and fracture. However, work hardening also reduces the ductility of the metal, making it more brittle. If a work-hardened metal is subjected to excessive stress or impact, it is more likely to fracture.

The extent of work hardening depends on several factors, including the amount of plastic deformation, the type of metal, and the temperature at which the deformation occurs. Most ductile metals exhibit work hardening. Annealing, a heat treatment process, can be used to reverse the effects of work hardening by allowing dislocations to rearrange and reduce their density, thereby restoring the metal's ductility.