How does cold working make a metal stronger?

Cold working, or cold working, strengthens a metal by inducing plastic deformation at temperatures below its recrystallization point. This process, often referred to as work hardening, relies on the metal's internal crystalline structure.12

When a metal is subjected to physical processes like rolling, forging, or drawing, the deformation occurs through the generation and movement of line defects known as dislocations along specific slip planes. As these dislocations move and intersect with one another, they form complex tangles. These tangles act as obstacles that inhibit further movement of dislocations, effectively locking the crystalline structure in place.23

Because the strength of a metal is largely determined by its resistance to this internal slippage, the accumulation of these intersecting dislocation lines makes the material harder and stronger, often doubling or tripling its yield stress. However, because this process relies on creating these internal barriers, there is a physical limit to how much a metal can be cold-worked before it becomes too brittle and risks cracking.321