Characterization of prior cold worked and age hardened Cu-3Ti-1Cd alloy

The influence of cold deformation by 50%, 75% and 90% on the age-hardening behavior of a Cu-3Ti-1Cd alloy has been investigated by hardness, tensile tests and light optical as well as transmission electron microscopy. The hardness of Cu-3Ti-1Cd alloy increased from 111 Hv in the solution-treated condition to 355 Hv in 90% cold worked and peak aged condition. The yield and ultimate tensile strengths of Cu-3Ti-1Cd alloy reached maxima of 922 MPa and 1035 MPa, respectively, on 90% deformation and peak aging. The microstructure of the deformed alloy exhibited elongated grains and deformation bands. The maximum strength on peak aging was brought about by the precipitation of ordered, metastable, coherent β′ Cu4Ti phase, in addition to high dislocation density and deformation twins. Both the hardness and the strength of the alloy decreased on overaging due to the development of the incoherent equilibrium phase β Cu3Ti in a cellular structure form. However, the morphology of the discontinuous precipitation was changed to globular form at high deformation levels.