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The first time that A15 structure was observed was in 1931 when an electrolytically deposited layer of tungsten was examined. [2] Discussion of whether the β-tungsten structure is an allotrope of tungsten or the structure of a tungsten suboxide was long-standing, but since the 1950s there has been many publications showing that the material is a true allotrope of tungsten.
TTT diagram of isothermal transformations of a hypoeutectoid carbon steel; showing the main components obtained when cooling the steel and its relation with the Fe-C phase diagram of carbon steels. Austenite is slightly undercooled when quenched below Eutectoid temperature. When given more time, stable microconstituents can form: ferrite and ...
The crystal structure of titanium at ambient temperature and pressure is close-packed hexagonal α phase with a c/a ratio of 1.587. At about 890 °C, the titanium undergoes an allotropic transformation to a body-centred cubic β phase which remains stable to the melting temperature.
The phase diagram shows, in pressure–temperature space, the lines of equilibrium or phase boundaries between the three phases of solid, liquid, and gas. The curves on the phase diagram show the points where the free energy (and other derived properties) becomes non-analytic: their derivatives with respect to the coordinates (temperature and ...
The unit cell of beta-tungsten. Beta-tungsten (β-W) is a metastable phase of tungsten widely observed in tungsten thin films.While the commonly existing stable alpha-tungsten (α-W) has a body-centered cubic structure, β-W adopts the topologically close-packed A15 structure containing eight atoms per unit cell, [1] [2] and it irreversibly transforms to the stable α phase through thermal ...
A generic phase diagram with unspecified axes; the invariant point is marked in red, metastable extensions labeled in blue, relevant reactions noted on stable ends of univariant lines. This rule is geometrically sound in the construction of phase diagrams since for every metastable reaction, there must be a phase that is relatively stable. This ...
Electron-beam physical vapor deposition, or EBPVD, is a form of physical vapor deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum. The electron beam causes atoms from the target to transform into the gaseous phase.
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