Aging behavior of Cu-Ni-Si alloy

Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM) were employed to study the microstructure and transformation of Cu-Ni-Si alloy. In Cu-1.0Ni-0.25Si-0.1Zn (wt.%) alloy, the precipitate responsible for the age-hardening effect was the delta-Ni2Si originating in nucleation process. On aging at the temperature below similar to773 K in Cu-3.2Ni-0.75Si-0.3Zn (wt.%) alloy, there were three different transformation products: a modulated structure resulting from spinodal decomposition, a (Cu, Ni)(3)Si with DO22 ordering structure nucleating from the modulated structure, and a delta-Ni2Si phase with disc-like structure appearing in (Ni, Si)-rich regions. On aging at the temperature above similar to773 K, the transformation products were grain boundary and intragranular precipitations of delta-Ni2Si. The free energy versus composition curves were employed to further explain the experimental observations. (C) 2003 Elsevier B.V. All rights reserved.