Grain boundary segregation
The enrichment of foreign atoms or alloying elements at crystallite boundaries increases bond strength and can prevent cracks.
Physical-Chemical Mechanism of Action
Grain boundary segregation refers to the concentration of foreign atoms or alloying elements at crystallite boundaries. This enrichment can arise from diffusion processes during welding or cooling.
Metallurgical Relevance & Welding Risks
Increased grain boundary segregation can improve weld strength and toughness by increasing bond strength between crystallites. This prevents cracks and improves the structure. However, excessive segregation can lead to excessive hardness, impairing formability and toughness.
Shop Practice & Action Instructions
To achieve optimal grain boundary segregation, set the welding process to allow sufficient time for diffusion of foreign atoms at grain boundaries. Control this through appropriate cooling time and temperature. A t8/5 value between 10 and 20 seconds is often suitable for good grain boundary segregation.