Formation mechanism of periodic layered structure in Ni_3Si/Zn system

Ni_3Si/Zn体系中周期型层片组织的形成机理(英文)

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,γphase 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.

利用SEM-EDS、FESEM和XRD研究Ni3Si/Zn固-气扩散偶和Ni3Si/Zn固-液扩散偶中周期型层片组织的形成。结果表明,固-液反应中的扩散通道为Ni3Si/(T+γ)/γ/…T/γ/Ni4Zn12Si3/γ/…Ni4Zn12Si3/γ/Ni4Zn12Si3/δ…/Ni4Zn12Si3/δ/Zn(液);固-气反应中的扩散通道为Ni3Si/θ/(T+γ)/γ/…/T/γ/…T/γ/Zn(气)。随着锌扩散流量的增大,扩散通道向富锌方向移动,Ni3Si基体与其最近邻的周期型层片对之间的距离减小。在周期型层片组织形成的初始阶段,γ相在T相基体中不断形核并长大,为降低表面能,最后变为连续的带状组织。根据实验结果和扩散动力学理论分析,探讨Ni3Si/Zn体系中周期型层片显微组织差异的形成原因和形成机理。