What is cold working?

Cold working refers to the plastic deformation of metals that occurs at temperatures below their recrystallization temperature. This process enhances the metal's strength and hardness through dislocation movements and is performed without the application of heat. When a metal is subjected to forces that exceed its yield strength, it deforms but does not return to its original shape, resulting in changes to the grain structure and an increase in tensile strength.

This option accurately captures the essence of cold working, emphasizing the significance of the deformation happening at lower temperatures, which is crucial for both the mechanical properties and the process design in manufacturing.

In contrast, the other options describe processes or techniques that either involve heat or are unrelated to the concept of cold working. Heating metals, for instance, pertains to hot working, which is fundamentally different since it involves reshaping materials while they are above their recrystallization temperature. Similarly, the strengthening of metals via heat treatment speaks more to processes like annealing or tempering, rather than cold working itself. Lastly, eliminating defects in metal structures can relate to various techniques, but it does not specifically define the cold working process, as that term focuses on deformation without heat.