| Certain spring applications require a material with a combination of high strength, stiffness, and electrical conductivity. An alloy, Cu-15wt%Ni-8wt%Sn, formed via a powder metallurgy process, is one of several copper-based alloys which can be heat treated/processed to form a metallic nano-structured alloy with good combinations of yield strength and electrical conductivity. For certain heat treatment conditions, this alloy decomposes spinodally from a face centered cubic disordered phase to form tin-rich and tin-lean composition fluctuations that are 10-100nm thick. Additional time at temperature produces ordering of the tin-rich regions. Uniaxial tensile tests have been used to identify the aging conditions with the highest yield strength. The uniaxial tensile and fully-reversed, flexural fatigue properties of the various heat-treated conditions were compared with observed fracture surfaces to characterize the failure mechanisms of the various time and temperature evolved microstructures. The mechanical properties have been correlated with structural information obtained from a variety of different techniques. Optical metallography, transmission electron microscopy, resistivity. |
