Eutectic

The eutectic point is the point at which a homogeneous mixed-phase (e.g., a eutectic alloy ) passes directly from the solid to the liquid state. The result is not composed of different phases melt.

At the eutectic point, the lowest solidification temperature of the binary system is available. In the phase diagram, it is the intersection of the liquidus and solidus line. In a silver-copper mixture ( Ag-Cu ), it is for example a mass fraction of 71.5 % silver and 28.5 % copper.

Also in the production of aluminum by igneous electrolysis, a eutectic mixture is used. Here (melting point 2058 ° C) and 89.5 % cryolite (melting point ~ 1000 ° C ) produced a mixture of melting point 950 ° C of 10.5 % (by ​​weight ) alumina.

The eutectic point of the iron is 4.3 mass percent carbon and 1 147 ° C. At this point, the melt decomposes into ledeburite. Another conversion ( the eutectoid transformation ) will be held at 0.80 weight percent C and 723 ° C. There is formed from the solid austenite two-phase, pearlite which consists of alternately arranged lamellar ferrite and cementite. These transformations are described in the iron-carbon diagram. The eutectoid decomposition thus provides a solid-state reaction Represents the counterpart to the eutectic reaction

In the chemical laboratory is made of the formation of low-melting eutectics to use to make freezing mixtures.