Obstacle density
The number of crystal dislocations and precipitates per unit volume that hinder plastic deformation. It is directly correlated with hardness and strength.
Physical-Chemical Mechanism of Action
The obstacle density refers to the number of crystal structure defects (like dislocations or precipitates) per unit volume in a metal. These obstacles can hinder the plastic deformation process because they make it harder for atoms to move within the crystal.
Metallurgical Relevance & Risks in Welding
A high obstacle density can lead to increased hardness and strength. However, this can also make the material more susceptible to cracks, especially under high loads or temperature changes. During weld formation, too high an obstacle density can lead to glass-hard martensite and hot cracking.
Workshop Practice & Instructions
To minimize the risks of too high obstacle density, it's important to carefully control the melting and cooling process. Too rapid cooling can promote the formation of martensite, while too slow cooling can coarsen the structure and reduce toughness. When selecting the welding process, make sure it's suitable for the specific metal to achieve an optimal obstacle density.