Töökõvenemine

Töökõvenemine, a term originating from Estonian, translates to "work hardening" or "strain hardening" in English. It refers to the phenomenon where a metal becomes stronger and harder when it is plastically deformed. This strengthening occurs because the deformation process introduces dislocations within the metal's crystal structure. These dislocations are line defects that impede the movement of other dislocations. As more deformation occurs, the density of dislocations increases, leading to more entanglement and a greater resistance to further movement. Consequently, the metal requires a higher stress to continue deforming, making it harder and stronger.

The process of work hardening is utilized in various manufacturing applications. For example, bending, drawing, or rolling metal can significantly increase its yield strength and tensile strength. This is often desirable for applications requiring increased durability and resistance to wear. However, work hardening also comes with a drawback: it reduces the ductility of the metal. Ductility is the ability of a material to deform plastically without fracturing. As a metal becomes harder and stronger through work hardening, it becomes more brittle and prone to cracking under stress.

To counteract the loss of ductility, metals that have undergone work hardening can be subjected to annealing, a heat treatment process. Annealing softens the metal by allowing dislocations to rearrange and reduce their density, thereby restoring some of its ductility. Work hardening is a fundamental concept in materials science and engineering, influencing the design and manufacturing of countless products.