Official Answer
Answer
Beryllium Copper (Alloy 25 / UNS C17200) is used for spiral retaining rings when high electrical conductivity and non-magnetic properties are required, such as in EMI/RFI shielding or MRI machines. CuBe can be heat-treated to reach a tensile strength of $160-200$ ksi, comparable to some steels. The material's modulus $E \approx 19 \times 10^6$ psi is lower than steel, which allows for easier installation into deep grooves without permanent deformation. However, processing must be handled carefully due to the toxicity of beryllium dust (though the solid alloy is safe). In electronics, these rings are often 'Gold' or 'Silver' plated to further enhance surface conductivity and prevent oxidation.
