Beryllium copper (BeCu), also known as copper beryllium, beryllium bronzeand spring copper, is a copper alloy with 0.5—3% beryllium and sometimes with other alloying elements. Beryllium copper combines high strength with non-magnetic and non-sparking qualities. It has excellent metalworking, forming and machining qualities. It has many specialized applications in tools for hazardous environments, musical instruments, precision measurement devices, bullets, and aerospace. Beryllium-containing alloys create an inhalation hazard during manufacturing due to their toxic properties.
Beryllium copper is a ductile, weldable, and machinable alloy. It is resistant to non-oxidizing acids (for example, hydrochloric acid, or carbonic acid), to plastic decomposition products, to abrasive wear and to galling. Furthermore, it can be heat-treated to improve its strength, durability, and electrical conductivity. Beryllium copper attains the highest strength (to 1,400 MPa (200,000 psi)) of any copper-based alloy.
Alloy 25 beryllium copper (C17200 & C17300) is an age-hardening alloy which attains the highest strength of any copper base alloy. It may be age hardened after forming into springs, intricate forms or complex shapes. It has superb spring properties, corrosion resistance and stability as well as good conductivity and low creep.
Tempered beryllium copper is Alloy 25 (C17200 & C17300) that has been age hardened and cold drawn. No further heat treatment is necessary except for a possible light stress relief. It is sufficiently ductile to wind on its own diameter and can be formed into springs and most shapes. Tempered wire is most useful where the properties of beryllium copper are desired, but age hardening of finished parts is not practical.
Alloys 3 (C17510) and 10 (C17500) beryllium copper are age-hardenable and provide excellent electrical conductivity in combination with good physical properties and endurance strength. Provided in either the age-hardenable condition or as tempered ware, they are used in springs and wire forms which are electrical conductors, or where retention of properties at elevated temperatures is important.
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. The thermal conductivity of these alloys lies between steels and aluminium. The cast alloys are frequently used as material for injection molds. The wrought alloys are designated by UNS as C17200 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 an hour, facilitating precipitation of metastable beryllidecrystals in the copper matrix. Overaging is avoided, as an equilibrium phase forms that depletes the beryllide crystals and reduces the strength enhancement. 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