työstökovettumiseksi

Työstökovettuminen, also known as work hardening or strain hardening, is a phenomenon observed in metals and alloys where they become harder and stronger when subjected to plastic deformation. This process occurs at temperatures well below the metal's melting point. When a metal is deformed, such as through bending, drawing, or rolling, the internal crystalline structure undergoes changes. Specifically, the dislocations, which are line defects within the crystal lattice, move and multiply. These dislocations can interact with each other, forming tangles and obstacles that impede further dislocation movement. As more dislocations accumulate and their movement becomes restricted, the metal resists further deformation, leading to an increase in its hardness and yield strength.

The extent of work hardening depends on several factors, including the type of material, the amount of deformation, and the temperature at which the deformation occurs. Different metals exhibit varying degrees of work hardening. For instance, some alloys are specifically designed to benefit from this process to achieve desired mechanical properties. While work hardening increases strength and hardness, it typically reduces the ductility and toughness of the material, making it more brittle. This trade-off is an important consideration in material selection and manufacturing processes. Annealing, a heat treatment process, can be used to reverse the effects of work hardening by allowing dislocations to annihilate or rearrange themselves, restoring the metal's ductility.