The main consequence of cold working on the mechanical properties of metals is that it increases strength but decreases ductility.

- Cold working, also known as work hardening, involves deforming a metal plastically at temperatures below its recrystallization point.
- This process introduces a high density of dislocations within the metal's crystal structure.
- The interaction and entanglement of these dislocations hinder the movement of other dislocations, thereby increasing the metal's strength and hardness.
- However, as the metal becomes stronger, it also becomes less capable of deforming plastically, which leads to a reduction in ductility.
- This trade-off between strength and ductility is a critical consideration in metal forming and mechanical design.

Important points:
- Cold working increases the dislocation density in metals.
- Movement of dislocations is hindered, resulting in higher strength and hardness.
- Ductility decreases because the metal becomes less able to deform plastically.
- The process does not significantly improve corrosion resistance or electrical conductivity.
- Tensile strength generally increases rather than decreases during cold working.

Reference: Callister, W.D., Jr., Materials Science and Engineering: An Introduction, 9th Edition, Chapter 6: Mechanical Properties of Metals and Alloys / Page 234-236