meltphase

Melt phase refers to the liquid state of a material that occurs when a solid substance is heated above its melting temperature. In crystalline materials, melting involves a transition from an ordered solid to a disordered liquid, and the melt phase is typically a homogeneous liquid whose properties depend on composition and pressure. In polymers and some alloys, the melt phase can be highly viscous and non-Newtonian, and crystalline regions may melt while amorphous regions remain mobile to varying degrees depending on crystallinity and temperature.

In metals and inorganic compounds, melting often occurs over a relatively narrow temperature range, yielding a clear solid-to-liquid transition that enables processes such as casting, forging, and welding. In many alloys, there is a solidus and a liquidus temperature, and between them the material may exist as a mixture of solid and liquid in a mushy region. Some materials exhibit incongruent or polymorphic melting, where different components melt or transform at different temperatures, leading to complex melt-phase behavior.

The melt phase is central to processing and materials design. Thermal analysis techniques, such as differential scanning calorimetry and thermomechanical analysis, are used to determine melting temperatures, enthalpies of fusion, and melt viscosity. These properties influence processing methods like extrusion, injection molding, and casting, as well as the resulting microstructure and performance of the material.

In geological contexts, partial melting of rocks in the Earth's interior creates melt fractions that affect geophysical and geochemical processes. Across disciplines, understanding the melt phase helps in interpreting phase diagrams, optimizing manufacturing, and predicting material behavior under elevated temperatures.