Correlation among microstructure,strength, and electrical conductivity of Cu-Ni-Be alloy

The UNS C17510 commercial Cu-Ni-Be alloy was heat treated in three different ways: AT, simple aging; HT, aging in the hardened condition; and TMT, a special thermo-mechanical treatment. It was found that in the electrical conductivity range of 50 to 60 pct IACS the TMT treatment results in a much higher yield strength than either the AT or the HT treatments. Three types of particles have been identified: relatively large primary beryllides, very small -γ precipitates, and small non-coherent nickel-rich beryllides (NRB). Based on measurements of the size distribution of NRB pre-cipitates and by means of an existing theoretical model, it was shown that these precipitates together with a dense dislocation network are responsible for the increased strength of the alloy follow-ing TMT.