Work Hardening
Strain hardening increases the hardness and strength of a metal through cold working, as dislocation density rises. However, the material loses its formability.
Physical-Chemical Mechanism of Action
Strain hardening occurs when a metal is plastically deformed under mechanical stress (e.g., during cold working). This leads to an increased dislocation density within the crystal. The dislocation bands and jogs block the movement of atoms, increasing hardness and strength.
Metallurgical Relevance & Welding Risks
In the weld, strain hardening can lead to an increased stress state. This can cause cracking or hot cracking in the material if the dislocation density becomes too high. Additionally, the increased hardness can make welding more difficult and impair the toughness of the material.
Workshop Practice & Instructions
To minimize strain hardening, a low stress or a long forming time should be chosen during cold working. When welding, it is important to monitor the dislocation density in the material and, if necessary, reduce it through appropriate forming or another processing method.