# Thermal expansion during the course of melting (in metals specifically)

The question is with regards to Thermal Expansion at the point of melting.

My basic understanding is that a material will generally undergo linear thermal expansion until some phase change occurs (crystal formation, melt, etc) that changes the material behavior. Take Aluminum, for example. It has a linear expansion coefficient of ~23E-6 /K when solid, but might go as high as ~98E-6 /K when melted. What I can't find, however, is how much expansion occurs over the process of the melting transition itself? It seems like if a solid metal with a poisson ratio of 0.35 (compressible material) transitions to a liquid with poisson's ratio of ~0.5 (incompressible), there must be some large amount of expansion as it fully "decompresses" to that point. Kind of how water which we all learned in elementary school counter-intuitively expands when frozen, I would assume metal behaves more intuitively with a large expansion when melted.

Is there any formula to predict this expansion amount during melt, assuming all heat is contributing to phase transition and not increasing temperature?