työstökarkaisu

Työstökarkaisu, also known as work hardening or strain hardening, is a phenomenon in metallurgy where a metal becomes harder and stronger as it is plastically deformed. This occurs when dislocations, which are line defects in the crystal structure of the metal, move and interact with each other during deformation. As the deformation continues, the dislocations become tangled and impede each other's movement, requiring more stress to cause further plastic flow.

The process of työstökarkaisu is commonly encountered during metalworking operations such as rolling, forging, drawing, and machining. For instance, repeatedly bending a paperclip will cause it to become stiffer and eventually break, demonstrating the effects of työstökarkaisu. This hardening can be beneficial in applications where increased strength and wear resistance are desired. However, it can also present challenges, making subsequent deformation more difficult and potentially leading to premature tool wear during machining.

The extent of työstökarkaisu depends on several factors, including the type of metal, the amount of deformation, and the temperature at which the deformation occurs. Different metals exhibit varying degrees of work hardening. For example, some aluminum alloys and copper alloys are more susceptible to työstökarkaisu than some steels. Annealing, a heat treatment process, can be used to reverse the effects of työstökarkaisu by allowing dislocations to rearrange and reduce their density, thereby softening the metal.