Abstract:The formation of periodic layered structure in Ni₃Si/Zn diffusion couples with Zn in vapor or liquid state was investigated by SEM-EDS, FESEM and XRD. The results show that the diffusion path in solid-liquid reaction is Ni₃Si/(T+γ)/γ/…T/γ/Ni₄Zn₁₂Si₃/γ/…Ni₄Zn₁₂Si₃/γ/Ni₄Zn₁₂Si₃/δ…/Ni₄Zn₁₂Si₃/δ/liquid-Zn, and the diffusion path in solid-vapor reaction is Ni₃Si/θ/ (T+γ)/γ/…/T/γ/…T/γ/vapor-Zn. With increasing Zn diffusion flux, the diffusion reaction path moves toward the Zn-rich direction, and the distance from the Ni₃Si substrate to the periodic layer pair nearest to the interface decreases. In the initial stage of both reactions, γ phase nucleates and grows within T matrix phase at first, and then conjuncts together to form a band to reduce the surface energy. Based on the experimental results and diffusion kinetics analysis, the microstructure differences were compared and the formation mechanism of the periodic layered structure in Ni₃Si/Zn system was discussed.

Key words: Ni₃Si; Zn; periodic layered structure; interface; diffusion