Partition coefficient
The segregation coefficient indicates how strongly an element tends to separate during solidification. It is the ratio of the concentration in the solid to that in the melt.
Physical-Chemical Mechanism of Action
The segregation coefficient (Sk) describes how strongly an element tends to separate during cooling. It's the ratio of the element's concentration in the solid to that in the melt under thermodynamic equilibrium.
Metallurgical Relevance & Welding Risks
A high segregation coefficient means the element segregates strongly. This can lead to uneven distribution in the weld, causing porosity or structural irregularities. In highly segregating alloys, this can improve toughness and properties, but if segregation is unfavorable, it can cause cracks and distortion.
Shop Practice & Action Items
To minimize segregation, ensure even cooling of the weld. Use proper shielding gas mixtures and avoid rapid cooling steps. In highly segregating alloys, you can increase cooling rate to achieve desired segregation.