Constitutional supercooling zone
The constitutional undercooling region is the area ahead of the solidification front where the local temperature is below the liquidus temperature and unstable crystallization occurs.
Physicochemical mechanism of action
In the constitutional supercooling zone, the local temperature is below the liquidus temperature, leading to unstable, dendritic crystallization. The chemical composition varies in this region, affecting the crystal structure.
Metallurgical relevance & welding risks
This unstable crystallization can cause fine grains and uneven structure. This increases the risk of hot cracking and reduces weld strength. It can also cause porosity, affecting the toughness of the material.
Shop practice & action items
Controlled cooling is crucial to minimize risks in the constitutional supercooling zone. This can be achieved by selecting the right welding process and parameters. In high-performance methods like TIG or MIG, the cooling rate should be regulated to ensure a uniform crystal structure.