Eutektika

Eutektika is a term used in materials science and geology to describe eutectic mixtures and their crystallization behavior. The word derives from Greek, meaning a melting together of components at a single temperature.

In a binary phase diagram, the eutectic point is the composition at which the liquid can transform at a single, invariant temperature into two (or more) solid phases simultaneously. A eutectic alloy has the lowest melting temperature among all mixtures of its constituents.

The solidification gives a characteristic microstructure in which the two phases grow cooperatively, forming fine lamellae or rod-like intergrowths known as a eutectic microstructure. The exact arrangement depends on growth conditions and constituent systems.

Common examples include the tin–lead solder with a eutectic composition of about 63% tin and 37% lead, melting at 183°C, and the iron–carbon system where the eutectic composition (about 4.3% carbon) at 1147°C yields liquid transforming to a mixture of austenite and cementite (ledeburite). Eutectics are important for soldering, casting, and alloy design, because they provide predictable melting behavior and fine-grained microstructures.

In geology and petrology, eutectic textures can occur when melts crystallize two minerals simultaneously at a eutectic temperature, leading to intergrowth textures in igneous rocks or metamorphic assemblages. Distinctions: eutectic refers to liquid-phase reactions; eutectoid refers to solid-state transformations (for example, austenite to pearlite in steel).