Investigation of periodic-layered structure in Zn/CuxTiy systems

Diffusion couples Zn/CuxTiy were prepared by the melting contact method and then annealed at 663K for various times. Using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), we discovered 7 new systems, i.e. Zn/Cu9Ti, Zn/Cu4Ti, Zn/Cu2Ti, Zn/Cu7Ti3, Zn/Cu3Ti2, Zn/Cu11Ti9 and Zn/Cu9Ti11, which can form the interesting periodic-layered structure within the reaction zones. By the traditional metallographic treatment and the in-situ section observation method respectively, it was confirmed that the periodic-layered structure is really composed of the CuZn2 singer-phase and the (CuZn2+TiZn3) two-phase layers distributing alternately within the reaction front area. Furthermore, the thickness of the periodic layers relates to the composition of Cu-Ti substrates: the higher content of Cu atoms in C--Ti alloy substrates, the thinner the layers will be. The experimental results are in accordance to the prediction of the diffusion-induced stresses model.