Reactive diffusion between solid Fe and liquid Zn was experimentally examined using Fe/Zn diffusion couples prepared by an immersion technique. Using this technique, a pure iron sheet was immersed in a molten pure Zn bath with a constant temperature of T= 723 K (450°C) for various times up to t=7.2×103 s (2 h). The microstructure of the cross section of the Fe/Zn diffusion couple was observed by scanning electron microscopy, and the chemical composition of each phase was determined by electron probe microanalysis. Interface concentrations of Fe for the ζ-FeZn13 and δ-FeZn7-10 phases at the ζ;/δ interface, c ζδ and cδζ. and for the liquid-Zn (L) phase at the ζ/L interface, cLζ, determined from the diffusion couples were found to be extremely higher than the corresponding equilibrium values, especially in the early stage of t<300 s, and the difference gradually decreased during immersion. The deviations from the equilibrium values for the cζδ and cLζ were proportional to the interdiffusion flux across the ζ phase layer.
- Phase diagram