Töökarastamine

Töökarastamine, often translated as work hardening or strain hardening, is a metallurgical phenomenon where a metal becomes stronger and harder as it is plastically deformed. This process involves introducing dislocations, which are line defects in the crystal structure of the metal. As deformation continues, these dislocations interact and impede each other's movement. The increased resistance to dislocation movement results in a higher yield strength and ultimate tensile strength for the material.

The effect of work hardening is achieved through various mechanical processes such as rolling, drawing, forging, and hammering. During these operations, the metal is permanently reshaped, leading to a microscopic rearrangement of its crystalline structure. While work hardening increases strength and hardness, it typically comes at the expense of ductility and toughness, making the material more brittle.

The degree of work hardening depends on the amount of plastic deformation. More deformation generally leads to greater hardening. This phenomenon is utilized in many manufacturing applications where increased strength is desired without adding significant weight or altering the material's composition. For example, steel wires used in cables or springs are often work hardened to improve their tensile strength.

Work hardening can be reversed through a process called annealing, which involves heating the metal to a specific temperature and then cooling it slowly. Annealing allows the dislocations to move and rearrange themselves, restoring the metal's ductility and reducing its hardness. Understanding work hardening is crucial for engineers and metallurgists in selecting and processing materials for various applications.