Liquidus

Liquidus temperature curve in the binary glass system SiO₂-Li₂O, based on 91 published data collected in SciGlass; model fit from Glassproperties.com

The liquidus temperature, T_L or T_liq specifies the temperature above which a material is completely liquid,^[1] and the maximum temperature at which crystals can co-exist with the melt in thermodynamic equilibrium. It is mostly used for impure substances (mixtures) such as glasses, alloys and rocks.

Above the liquidus temperature the material is homogeneous and liquid at equilibrium. Below the liquidus temperature, more and more crystals will form in the melt if one waits a sufficiently long time, depending on the material. Alternately, homogeneous glasses can be obtained through sufficiently fast cooling, i.e., through kinetic inhibition of the crystallization process.

The crystal phase that crystallizes first on cooling a substance to its liquidus temperature is termed primary crystalline phase or primary phase. The composition range within which the primary phase remains constant is known as primary crystalline phase field.

The liquidus temperature is important in the glass industry because crystallization can cause severe problems during the glass melting and forming processes, and it also may lead to product failure.

The liquidus temperature can be contrasted to the solidus temperature. The solidus temperature quantifies the point at which a material completely solidifies (crystallizes). The liquidus and solidus temperatures do not necessarily coincide; if a gap exists between the liquidus and solidus temperatures, then within that gap, the material consists of solid and liquid phases simultaneously (like a slurry).

For pure substances, e.g. pure metal, pure water, etc. the liquidus and solidus are at the same temperature, and the term "melting point" may be used. For impure substances, e.g. alloys, tap water, coca cola, ice cream, etc. the melting point broadens into a melting interval instead. If the temperature is within the melting interval, one may see "slurries" at equilibrium, i.e. the slurry will neither fully solidify nor melt. This is why new snow of high purity either melts or stays solid, while dirty snow on the ground tend to become slushy at certain temperatures. Weld melt pools containing high levels of sulfur, either from melted impurities from the base metal or from the welding electrode, typically have very broad melting intervals, which leads to increased risk of hot cracking.

Glass science topics

Basics	Glass Glass transition Supercooling

Glass formulation	AgInSbTe Bioglass Borophosphosilicate glass Borosilicate glass Ceramic glaze Chalcogenide glass Cobalt glass Cranberry glass Crown glass Flint glass Fluorosilicate glass Fused quartz GeSbTe Gold ruby glass Lead glass Milk glass Phosphosilicate glass Photochromic lens glass Silicate glass Soda-lime glass Sodium hexametaphosphate Soluble glass Tellurite glass Ultra low expansion glass Uranium glass Vitreous enamel Wood's glass ZBLAN

Glass-ceramics	Bioactive glass CorningWare Glass-ceramic-to-metal seals Macor Zerodur

Glass preparation	Annealing Chemical vapor deposition Glass batch calculation Glass forming Glass melting Glass modeling Ion implantation Liquidus temperature Sol-gel technique Viscosity Vitrification

Optics	Achromat Dispersion Gradient-index optics Hydrogen darkening Optical amplifier Optical fiber Optical lens design Photochromic lens Photosensitive glass Refraction Transparent materials

Surface modification	Anti-reflective coating Chemically strengthened glass Corrosion Dealkalization DNA microarray Hydrogen darkening Insulated glazing Porous glass Self-cleaning glass Sol-gel technique Toughened glass

Diverse topics	Glass-coated wire Safety glass Glass databases Glass electrode Glass fiber reinforced concrete Glass ionomer cement Glass microspheres Glass-reinforced plastic Glass-to-metal seal Porous glass Prince Rupert's Drops Radioactive waste vitrification Windshield

References

↑ Askeland, Donald R. & Wright, Wendelin J. (January 14, 2014) [1st. Pub. 2009]. Essentials of Materials Science and Engineering. Cengage Learning. p. 329. ISBN 978-1-11157685-1.

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Liquidus

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References