Eutectics


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Related to Eutectics: Eutectic temperature, Eutectic point

Eutectics

The microstructures that result when a solution of metal of eutectic composition solidifies. The eutectic reaction must be distinguished from eutectic microstructures. The eutectic reaction is a reversible transformation of a liquid solution to two or more solids, under constant pressure conditions, at a constant temperature denoted as the eutectic temperature. Microstructures which are wholly eutectic in nature can occur only for a single, fixed composition in each alloy system demonstrating the reaction.

Although technologically important alloy systems, particularly the Fe-C system (all cast irons used commercially pass through a eutectic reaction during solidification), exhibit at least one eutectic reaction, there has been little exploitation of wholly eutectic microstructures for structural purposes. Some eutectic fusible alloys are used as solders, as heat-transfer media, for punch and die mold and pattern applications, and as safety plugs. A silver-copper eutectic alloy is also used for high-temperature soldering applications. See Soldering

Directional solidification of eutectic alloys so as to create a microstructure well aligned parallel to the growth direction produces high-strength, multiphase composite materials with excellent mechanical properties. Among the major advantages of these alloys are extraordinary thermal stability of unstressed microstructures, retention of high strength to very close to the eutectic temperature of the respective alloys, and the ability to optimize strength by appropriate alloying additions to induce either solid-solution strengthening or intraphase precipitation of additional phases.

The most likely future applications for aligned eutectics are as gas turbine engine materials (turbine blades or stator vanes) or in nonstructural applications such as superconducting devices in which directionality of physical properties is important. See Alloy, Metal

References in periodicals archive ?
The three alternative eutectic systems investigated, namely the Al-Ni eutectic, the Al-Fe eutectic and the Al-Ni-Fe eutectic, exhibit very good casting ability and tensile properties at both room temperature and elevated temperature; and in this regard, they compare favorably with the Al-Si eutectic.
The Pd wire should not come into contact with silicious refractories as they may form a Pd-Si eutectic with a melting temperature of 816[degrees]C that weakens the wire.
Due to solidification after brazing the structure of the seam metal is formed, consisting of a high-alloy matrix solution over axes of dendrites, boundary developed carbide phases of eutectic type, and complex alloyed eutectics in the interphase areas.
When the solder alloy contains elements that can form more than one eutectic alloy, different shrinkage patterns can be formed that will give the solder joints a rough appearance.
Yang, "Design and thermal properties of a novel ternary chloride eutectics for high-temperature solar energy storage," Applied Energy, vol.
The two curves for the melting of aluminum and silicon meet at a eutectic at a composition of 12.6 weight percent silicon and a temperature of 1,071F (577C) (Fig.
Significant share of eutectic is present in the structure of high speed steel.
During solidification, the eutectic with the lowest melting point is often surrounded by already-solidified particles from the eutectics with the higher melting points.
Many research studies have been carried out to investigate the effect of ECPs on the solidification of pure metals [10], eutectic alloys [11-13], and solid solution alloys [14] in the past decades.
After introduction into a boron-containing brazing alloy of insignificant amount of silicon in the process of solidification in the matrix solution form both binary and triple eutectics. Binary eutectics represent [gamma]-Ni/Ni boride; [gamma]-Ni/ Ni silicide; [gamma]-Ni/Cr boride; triple--[gamma]-Ni/Ni boride/Cr boride and [gamma]-Ni/Ni boride/Ni silicide.
This new method was called appropriate mixing of binary eutectics. As far as now, several Zr-based [12], Ni-based [14], and Cu-based [15] bulk metallic glasses have been successfully developed based on this new approach, which thoroughly demonstrated its usefulness for searching new BMG compositions with high GFA.