Beryllium brittleness

As a light, strong metal, beryllium holds considerable promise as a useful engineering material, but because of an inherent directional brittleness, a really significant commercial use, e.g. in the aircraft industry, has not proved possible. It has been used to a limited extent in aerospace applications, and it was employed as heat shields for the Project Mercury space capsule. It has also found use in precision guidance systems when fairly pure environmental conditions can be assured. 

Beryllium is a light metal (s.g. 1 -85) with a hexagonal close-packed structure (axial ratio 1 568). The most notable of its mechanical properties is its low ductility at room temperature. Deformation at room temperature is restricted to slip on the basal plane, which takes place only to a very limited extent. Consequently, at room temperature beryllium is by normal standards a brittle metal, exhibiting only about 2 to 4% tensile elongation. Mechanical deformation increases this by the development of preferred orientation, but only in the direction of working and at the expense of ductility in other directions. Ductility also increases very markedly at temperatures above about 300°C with alternative slip on the 1010 prismatic planes. In consequence, all mechanical working of beryllium is carried out at elevated temperatures. It has not yet been resolved whether the brittleness of beryllium is fundamental or results from small amounts of impurities. Beryllium is a very poor solvent for other metals and, to date, it has not been possible to overcome the brittleness problem by alloying. 

As already indicated, the brittleness of beryllium has so far been the main determining feature in the technology, and because of the mechanical anisotropy, the most widely practised method of fabrication is via powder metallurgy. 

The early promise of wide applications for beryllium has not materialised, despite improvements in purity and more efficient means of consolidation such as isostatic hot pressing, because of the metal s toxicity, brittleness and cost. It is now chiefly of interest in the specialised fields of aerospace and nuclear applications. BrushWellman is currently the sole commercial primary producer of beryllium metal in the West. 

Beryllium is one-third as dense as aluminum. Fresh-cut surfaces of the metal oxidi2e, thus resisting further oxidation, as does aluminum. It is a hghtweight, hard, brittle metal. It can be machined (rolled, stretched, and pounded) into many shapes and is used to produce hghtweight alloys. 

Beryllium (Be) is a gray-colored brittle metal. Be bums in air to form BeO or B03N2, releasing a high heat of combustion. However, Be and its compounds are known as highly toxic materials. 

Close-packed hexagonal crystalline structure is a very brittle structure. It is found in metals that have little ductility. Examples of such metals are cadmium, cobalt, magnesium, titanium, beryllium, and zinc. These metals would not be desirable for jewelry fabrication. 

VH.16 BERYLLIUM, Be (At 9 01) Beryllium is a greyish-white, light but very hard, brittle metal. It dissolves readily in dilute acids. In its compounds beryllium is divalent, otherwise it resembles closely aluminium in chemical properties it also exhibits resemblances to the alkaline earth metals. The salts react acid in aqueous solution, and possess a sweet taste (hence the name glucinum formerly given to the element). Beryllium compounds are highly poisonous. 

In previous arrangements of the Periodic Table see Periodic Table Trends in the Properties of the Elements), the elements beryllium, magnesium, calcium, strontium, barium, and radium were referred to as members of Group Ila, or 2A. As inclusion of the word metaT in their title implies, these elements are both malleable and extrudable however, they are rather brittle. They are electrical conductors. When pure, all except the lightest, beryllium, react with atmospheric... 

PROP Pure beryllium is a hard, brittle, silvery metal. Mp 1278°, bp 2970°, d 1.85. Beryllium oxide white powder. Mp 2530°, d 3.0. Beryllium chloride white to faintly yellow powder, deliquescent. Mp 399°, bp 482°. Beryllium fluoride glassy, hygroscopic solid. Mp 545°, d 2.0. Beryllium nitrate white to slightly yellow crystals. Mp 60°). Beryllium sulfate Mp 550°. 

Beryllium and magnesium are greyish metals, while the remaining group 2 metals are soft and silver-coloured. The metals are malleable, ductile and quite brittle in air, the shiny surface of each metal quickly tarnishes. 

The grey metal is rather light (1.86 g/cm3) and quite hard and brittle. Since the absorption of electromagnetic radiation depends on the electron density in matter, beryllium has the lowest stopping power per unit mass thickness of all suitable construction materials and is used for windows in X-ray apparatus. It is also added as an antioxidant to copper and phosphor bronzes and as a hardener to copper. 

Beryllium bo- ri-le-om [NL, from Gk beryl-lion] (ca. 1847) n. A steel-gray light strong brittle toxic bivalent metallic element used chiefly ads a hardening agent in alloys. 

Sintered molybdenum (thermal conductivity around 115 W/mK) for nozzle casings and tips in applications up to 360 °C (Figure 4.5b), and for melts with an abrasive action (five times greater durability than that of copper/beryllium alloys). After ion treatment (thermo-implantation) the durability of molybdenum sinters is increased by many times. Molybdenum sinters are brittle in places where there is a notch, e.g., the thermocouple groove ... 

Materials. At these extremely low temperatures, ferrous metals become brittle and consequently cannot resist shock loads. In a cryogenic pump, elements having a low transition from the ductile to the brittle state, must be used. Such elements are aluminum, copper, silver, lead, nickel, and beryllium. 

In a scientific application of cryogenics, a liquid hydrogen bubble chamber located at the Cambridge Electron Accelerator failed on its initial cooldown due to brittle fracture of a beryllium beam port. The resulting fire and explosion was a major blow to the project. 

The properties of some materials are directly related to their crystal structures. For example, pure and undeformed magnesium and beryllium, having one crystal structure, are much more brittle (i.e., fracture at lower degrees of deformation) than are pure and undeformed metals such as gold and silver that have yet another crystal structure (see Section 7.4). 

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