Scheil equation
The Scheil equation describes the distribution of alloying elements during cooling. In the liquid, everything mixes well, but in the solid it does not.
Physical-Chemical Mechanism of Action
The Scheil equation models how chemical elements in a metal redistribute during cooling. In the liquid state, alloying elements mix completely, while in the solid state no further diffusion takes place.
Metallurgical Relevance & Risks in Welding
Uneven cooling can lead to Scheil segregation, where certain elements concentrate at the boundaries. This causes inconsistent properties and increases the risk of cracking or failure.
Workshop Practice & Procedures
To avoid Scheil segregation, ensure uniform cooling. Use suitable welding processes like gas welding or plasma welding that allow rapid and uniform cooling. For heavy alloys, a post-weld heat treatment (PWHT) can be applied to normalize the chemical distribution.