Grain Boundary Segregation Tendency
Grain boundary segregation tendency is a thermodynamic process where accompanying and trace elements concentrate at grain boundaries. This locally reduces the cohesion of the microstructure and can lead to weak points.
Physical-Chemical Mechanism of Action
During welding or processing of metals, certain elements (impurities and trace elements) can concentrate at the boundaries between crystal cells (grain boundaries). This process, the grain boundary segregation tendency, occurs due to the thermodynamic tendency to minimize Gibbs energy. Elements like silicon or carbon can accumulate at grain boundaries and reduce the local cohesion of the metal.
Metallurgical Relevance & Risks in Welding
The segregation of impurities and trace elements can lead to weak points in the structure, such as hot cracks or reduced toughness. Especially in high-temperature processes like gas treatments or welding with high voltages, the grain boundary segregation tendency is an important factor for the quality of the weld.
Workshop Practice & Action Guidelines
To minimize the grain boundary segregation tendency, low voltages and controlled temperatures should be maintained during welding. For metals with high segregation tendency, carefully select the welding process and adhere to process parameters like temperature and time. If necessary, a post-weld treatment can be performed to reduce segregation.