Beryllium copper
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Beryllium copper, also known as copper beryllium or beryllium bronze, is a metal alloy that contains copper with 0.5-3% beryllium, sometimes with other alloying elements, has significant metalworking advantages and great operating performance qualities.
This is a highly ductile alloy which can be precisely stamped and shaped into a wide variety of complex patterns including very small yet critical parts. The addition of beryllium allows this alloy to be heat-treated into being a very strong and durable metal and also gives the alloy a high electrical conductivity. It is used in springs and to make other parts that need to retain their shapes over long periods of time while being subjected to repeated use. It is often used in the low-current contacts for batteries and connectors in electronics for consumer, industrial, and military use. Beryllium copper is also used as a material for making some molds in plastic manufacturing. The Protherm beryllium copper alloy, used for molds, contains 0.4% beryllium and 1.8% nickel.
High strength beryllium copper alloys contain up to 2.7% of beryllium (cast), or 1.6-2% of beryllium with about 0.3% cobalt (wrought). The high mechanical strength is achieved by precipitation hardening or age hardening. Their thermal conductivity lies between steels and aluminium. The cast alloys are frequently used as material for injection molds. The wrought alloys are designated by UNS as C172000 to C17400, the cast alloys are C82000 to C82800. The hardening process requires rapid cooling of the annealed metal, resulting in a solid state solution of beryllium in copper, which is then kept at 200-460 °C for at least a hour, facilitating precipitation of metastable beryllide crystals in the copper matrix, resulting in increase of the alloy strength. Overaging should be avoided, as an equilibrium phase forms that depletes the beryllide crystals and results in decrease of strength. The beryllides are similar in both cast and wrought alloys.
High conductivity beryllium copper alloys contain up to 0.7% beryllium, together with some nickel and cobalt. Their thermal conductivity is better than of aluminium, only a bit less than pure copper. They are usually used as electric contacts in connectors. [1]
Beryllium copper alloys are resistant to non-oxidizing acids (hydrochloric acid, carbonic acid, etc.) and other plastic decomposition products. They have good machinability, and can be welded. They are also resistant to abrasive wear and galling.
Beryllium copper is also frequently used in the manufacture of professional-quality percussion instruments, especially tambourine and triangle, where it is prized for its clear tone and strong resonance. Unlike most other materials, an instrument composed of beryllium copper will maintain a consistant tone and tambre for as long as the material resonates. The "feel" of such instruments is rich and melodious to the point that they seem hideously out of place when used inœ darker, more rhythmic pieces of classical music.