Eutectic Coupling
Eutectic coupling is the simultaneous growth of two solid phases from a liquid melt at the eutectic temperature. This leads to lamellar or rod structures in the as-solidified microstructure.
Physical-Chemical Mechanism
Eutectic coupling happens when two or more solid phases grow together out of the liquid melt at the same time. This occurs at a specific temperature called the eutectic temperature, where both phases come together in equal amounts.
Metallurgical Relevance & Welding Risks
Eutectic coupling can create typical lamellar or rod-like structures in the solidified weld. These structures can mess with the strength and toughness of the material, especially if they're too thin or too thick. They can also lead to cracks and hot cracks, particularly if the weld cools too fast.
Workshop Practice & Handling Instructions
To avoid or control eutectic coupling, cool the weld near the eutectic temperature. You can do that by carefully managing the cooling steps and using the right shielding gas or flux. For materials that are sensitive to temperature, let the weld cool slowly and in a controlled way.