Plastic Strain Hardening
Plastic deformation hardening is the process by which the hardness of a metal is increased through mechanical deformation. This occurs due to an increase in dislocation density in the crystal lattice.
Physical-Chemical Mechanism of Action
In plastic deformation hardening, atoms in the metallic crystal lattice are displaced under mechanical load. This leads to increased dislocation density, which impedes flow of the material structure and thus increases hardness.
Metallurgical Relevance & Risks in Welding
Plastic deformation hardening can lead to increased hardness of the material in the weld zone, which coarsens the microstructure and reduces toughness. This can lead to cracks or fractures in the material, especially if deformation is too severe.
Workshop Practice & Action Guidelines
To minimize plastic deformation hardening, low loads and slow cooling steps should be maintained during welding. The maximum hardness of the material should be controlled by holding temperature and time within the critical temperature window.