Third-Order Residual Stress State
Residual stress state of the third kind: Local lattice distortions around defects such as dislocations or vacancies, reflecting crystal lattice imperfections.
Physicochemical Mechanism of Action
Third-order residual stress states arise from localized lattice distortions in the immediate atomic vicinity of defects such as dislocations or vacancies. These distortions reflect the inherent imperfection of the crystal lattice and lead to stresses within the material.
Metallurgical Relevance & Risks in Welding
These localized stresses can lead to cracks or grain growth in the weld. At high temperatures during welding, the material can plastically deform, which increases stresses and affects the microstructure. This can lead to a fine-grained or glass-hard structure, which impairs the toughness and durability of the weld.
Workshop Practice & Action Guidelines
To minimize the risk of third-order residual stress states, careful pretreatment of the material before welding is important. This may include cleaning the surface and removing any dislocations or vacancies. Additionally, the welding process should be selected to allow for even deformation and minimize stresses in the material. For heavy materials, it is advisable to perform a slower cooling process to avoid the formation of localized stresses.