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How can work hardening increase the yield strength of a metal?

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Figure 1: The position vector x and the velocity vector v of a material point, the body force fdV acting on an element dV of volume, and the surface force TdS acting on an element dS of surface in a Cartesian coordinate system 1, 2, 3 (see text).
mechanics of solids Figure 1: The position vector x and the velocity vector v of a material point, the body force fdV acting on an element dV of volume, and the surface force TdS acting on an element dS of surface in a Cartesian coordinate system 1, 2, 3 (see text).

Work hardening, also known as strain hardening, increases the yield strength of a metal through the generation and interaction of dislocations, which are line defects within the metal's crystalline structure.12

When a metal undergoes plastic deformation—such as through rolling, forging, or drawing—these dislocations move along slip planes. As deformation continues, slip occurs on different planes, causing the dislocations to intersect and form complex tangles. These tangles act as obstacles that inhibit further movement of the dislocations. Because the continued motion of dislocations is required for the metal to deform plastically, creating these internal barriers effectively strengthens the material, often doubling or tripling its yield stress.231

In essence, the more the metal is deformed, the more these structural obstacles multiply, making it increasingly difficult for the crystal structure to slip and thereby raising the stress required to induce further permanent deformation.12