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Eutectoid

(I) An isothermal reversible reaction in which a solid solution is converted into two or more intimately mixed solids on cooling, the number of solids formed being the same as the number of components in the system. (2) An alloy having the composition indicated by the eutectoid point on an equilibrium diagram. (3) An alloy structure of intermixed solid constituents formed by a eutectoid reaction.

 

Elastic Limit

The maximum stress that a material is capable of sustaining without any permanent strain (deformation) remaining upon complete release of the stress.

 

Electron-Beam Heat Treating

A selective surface hardening process that rapidly heats a surface by direct bombardment with an accelerated stream of electrons.

 

Embrittlement

The severe loss of ductility or toughness or both, of a material, usually a metal or alloy. Many forms of embrittlement can lead to brittle fracture . Many forms can occur during thermal treatment or elevated-temperature service (thermally induced embrittlement). Some of these forms of embrittlement, which affect steels, include blue brittleness , 885 F (475 C) embrittlement , quench-age embrittlement , sigma-phase embrittlement , strain-age embrittlement , temper embrittlement , tempered martensite embrittlement , and thermal embrittlement . In addition, steels and other metals and alloys can be embrittled by environmental conditions (environmentally assisted embrittlement). The forms of environmental embrittlement include acid embrittlement, caustic embrittlement, corrosion embrittlement, creep-rupture embrittlement, hydrogen embrittlement, liquid metal embrittlement, neutron embrittlement, solder embrittlement, solid metal embrittlement, and stress-corrosion cracking.

 

Embrittlement - Stainless Steels

Embrittlement of stainless steels upon extended exposure to temperatures between 400 and 510 F). This type of embrittlement is caused by fine, chromium-rich precipitates that segregate at grain boundaries; time at temperature directly influences the amount of segregation. Grainboundary segregation of the chromium-rich precipitates increases strength and hardness, decreases ductility and toughness, and changes corrosion resistance. This type of embrittlement can be reversed by heating above the precipitation range.

 

Enantiotropy

The relation of crystal forms of the same substance in which one form is stable above a certain temperature and the other form stable below that temperature. Ferrite and austenite are enantiotropic in ferrous alloys.

 

Elapsed Time Meter

An instrument that indicates the time an electronic device or system has been in operation. Most such meters are based on electric clockwork that runs only while the system is in operation, holding the count during shutdown periods.

 

Earth Ground

1. A common connection to an electrode buried in the earth so that good conductivity is maintained between the common circuit point and the earth itself. 2. A rod driven into the surface of the earth for use as a common circuit connection.

 

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