Peening - Work Hardening

Work Hardening

Cold work also serves to harden the material's surface. This makes cracks less likely to form at the surface and provides resistance to abrasion. When a metal undergoes strain hardening its yield strength increases but its ductility decreases. Strain hardening actually increases the number of dislocations in the crystal lattice of the material. When a material has a great number of dislocations, plastic deformation is hindered, and the material will continue to behave in an elastic way well beyond the elastic yield stress of the non-strain hardened material.

Copper and other malleable metals respond well to strain hardening. Some forms of copper, such as ductile wire, are easily deformed, yet beaten copper articles are quite stiff. Strain hardening may be reversed by annealing.

Hand peening may be performed using a peening hammer. It is still used today in the hand manufacture of high quality cutting blades.

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