Periodic layer formation during solid state reaction between Zn and CuTi

The exact mechanism of the periodic layer formation during solid state reactions remains still a controversial topic.The exploration of new systems, especially the non-silicide systems, is very important for the understanding of the formation mechanism and even for the possible applications of this interesting structure. This paper reports the periodic-layered structure discovered in the reaction zone of the new reaction system Zn/CuTi annealed at 663 K for various times. The composition profile of the reaction zone and the chemistry of the periodic structure were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). It was found that the periodic-layered structure, consisting of the two-phase layer of (CuZn2 + TiZn3) and the single-phase layer of CuZn2 alternated within the reaction zone, would be dissolved gradually during the diffusion process. The formation mechanism of the periodic layers was explained well with the diffusion-induced stresses model.

Backscattered electron image of the reaction zone in the diffusion couple Zn/CuTi annealed at 663 K in vacumm for 24h. During the reactive diffusion, phase CuZn2 and phase TiZn3 in the periodic layers would be dissolved gradually into phase Ti1Cu2Zn14 (Ti5.6–6.4Cu10.1–12.4Zn81.3–84.3) and phase TiZn7 (Ti11.9–13.7Zn86.7~88.1), respectively.Figure optionsDownload as PowerPoint slideHighlights
► The mechanism of the periodic-layered structure remains a controversial topic.
► It is important to explore the new systems, especially the non-silicide systems.
► A new reaction system Zn/CuTi was discovered to form the periodic structure.
► The mechanism is explained well with the diffusion-induced stresses model.