1 Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
3 Beijing HAWAGA Power Storage Technology Company Ltd., Beijing 100085, China
4 Department of Solid State Physics, University of Debrecen, H-4010 Debrecen, Hungary
5 Institute for Nuclear Research, Hungarian Academy of Sciences, H-4001 Debrecen, Hungary
Cite this article:
Yu GONG, Yongchong CHEN, Dandan LIU, Yanping ZHANG, Csaba CSERHáTI, Attila CSIK. INVESTIGATION OF PERIODIC-LAYERED STRUCTURE DURING SOLID STATE REACTIONS OF Zn/CuxTiy SYSTEMS. Acta Metall Sin, 2016, 52(3): 349-354.
Periodic-layered structure during solid state reactions is one of the most complicated and interesting structures in the solids, which consists of a periodic sequence of layers that grow perpendicularly to the expected macroscopic diffusion flow. Since the Zn/Fe3Si system was first discovered, much research work has been done on the characterization of the microstructures, the understanding of the formation mechanism and discovery of new systems. However, the exact nature of this phenomenon still remains a controversial topic. In the spirit of thermodynamic instability mechanism, the periodic-layered structure consists of single phase α layer and single phase β layer arrange alternately, while in that of dynamic instability mechanism, which is based on a diffusion-induced stress model, the structure is considered to be composed of regular multilayers of single phase α and two-phase α+β. In the present work, the solid state reactions of various Zn/CuxTiy diffusion systems annealed at 663 K for different times were investigated by using melting contact method, SEM and EDS. The results show that both the polished sections and the in situ fracture surfaces of periodic-layered structure, 5 new systems, i.e. Zn/Cu9Ti, Zn/Cu4Ti, Zn/Cu7Ti3, Zn/Cu3Ti2, Zn/Cu4Ti3 are found to form periodic-layered structure within the diffusion zones. The periodic-layered structure is composed of the CuZn2 single phase and CuZn2+TiZn3 two-phase layers distributing alternately within the reaction area near the CuxTiy side. Furthermore, the thickness of the periodic layers relates to the composition of CuxTiy substrates: the higher the content of Cu atom in the Cu-Ti substrate, the thinner the layer will be. In addition, the adjacent two-phase layers show mated topography and the interface between the periodic layers illustrates typical tear characteristics in mechanics, which are in good accordance with the prediction of the diffusion-induced stresses model. Therefore, the present work provides new and convincing evidence for the dynamic instability mechanism in the interpretation of periodic-layered structures in solids.
Fund: Supported by Chinese-Hungarian Bilateral Project (No[2013]83-6-13), National Natural Science Foundation of China (No.51477170) and Beijing Natural Science Foundation (No.2142034)
Fig.1 SEM image of Zn/3Cu-2Ti diffusion couple after annealing at 663 K for 24 h
Fig.2 SEM images of reaction zone in Zn/3Cu-2Ti diffusion couple after annealing at 663 K for 24 h at low (a) and high (b) magnifications
Fig.3 SEM images of 6 new reaction systems producing periodic-layered structure in Zn/3Cu-2Ti diffusion couple after annealing at 663 K for 24 h (a) reaction zone containing Zn/Cu3Ti2, Zn/Cu7Ti3 and Zn/CuTi systems (b) reaction zone containing Zn/Cu3Ti2, Zn/Cu7Ti3, Zn/CuTi, Zn/CuTi2 and Zn/Cu4Ti systems (c) reaction zone containing Zn/Cu3Ti2 and Zn/Cu4Ti3 systems
Fig.4 SEM image of 3 new reaction systems (Zn/Cu9Ti, Zn/Cu7Ti3, Zn/Cu4Ti systems) producing periodic-layered structure in Zn/4Cu-Ti diffusion couple after annealing at 663 K for 24 h
Fig.5 SEM images of periodic-layered structure in the reaction zones of Zn/3Cu-2Ti diffusion couples after metallographic processing at low (a) and high (b) magnifications
Fig.6 Low (a) and high (b) magnified cross-sectional fracture, two-phase layer (c) and single phase layer (d) morphologies of periodic-layered structure in Zn/1Cu-1Ti diffusion couple after annealing at 663 K for 12 h
Fig7 Schematic of formation process of periodic-layered structure in Zn/Cu3Ti2 reaction system
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