Constitutional supercooling is a phenomenon that occurs during the solidification of a material, such as a metal alloy. When a material is cooled below its melting point, it typically begins to solidify by forming small crystals, or grains, of the solid phase. However, in some cases, the actual solidification temperature of the material can be lower than its melting point due to the presence of impurities or alloying elements.
Constitutional supercooling occurs when the solidification temperature of a material is lower than its melting point because the solid phase that forms during solidification has a different composition than the original liquid phase. This difference in composition can result in a lower solidification temperature, leading to the formation of a supercooled liquid phase.
In the context of metal alloys, constitutional supercooling can have important implications for the microstructure and properties of the final solidified material. It can affect the size, shape, and distribution of the grains in the material, as well as the presence of certain phases or precipitates. Understanding and controlling constitutional supercooling is therefore important for the design and processing of alloys with specific properties and performance characteristics.