Solvus line
The solvus line in the phase diagram shows the maximum solubility of an element in a solid solution at varying temperatures. Below it, the crystal stays homogeneous; above it, a second phase forms by precipitation.
Physical-Chemical Mechanism of Action
The solvus line is a boundary line in the phase diagram that shows the maximum solubility of an element in a solid solution as a function of temperature. Below this line, the element can be fully dissolved, and the crystal remains homogeneous. Above the solvus line, the element exceeds its maximum solubility limit, causing a second phase to form through precipitation of the excess element.
Metallurgical Relevance & Risks in Welding
The solvus line is critical for the strength and hardness of solid solutions. Exceeding the line can cause phase transformations, which can impair mechanical properties. Moreover, this can lead to welding defects such as porosity or inhomogeneity.
Workshop Practice & Action Instructions
To account for the solvus line in welding, it is important to precisely control welding temperatures and times. For solid solutions with a low solvus line, temperature control and cooling rate must be carefully managed to avoid phase transformations. Use special welding processes like gas shielded welding or controlled cooling for such materials.