Liquidus surface, significance

But the practice shows that only a small part of the submicroscopic particles (or so-called plankton ) are active. Most of the nonmetallic particles do not participate in the solidification process. Only the particles with deep cracks filled with a matrix alloy are sufficiently stable to serve as solidification sites [60]. The melting temperature of such an alloy appears to be significantly higher than that of the equilibrium liquidus. Filling of imperfections on the surface of nonmetallic inclusions is hampered by the presence of a gas phase within the imperfections, which does not allow the particles to serve as nucleation sites for the matrix and intermetallics. 

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