Inhibitory effect of Ti and La on Fe dissolution in Al-Zn-Si bath by in-situ SXRD, SXRF, TEM and DFT calculation

During the hot-dipping process, there is always a desire to restrain the mutual diffusion between steel and alloy bath for suppressing the formation of bath dross. However, the dissolution of steel sheets is difficult to quantify by the traditional methods. In this work, in-situ X-ray diffraction was used to investigate the solid-liquid reaction between solid Fe and Al-Zn-Si liquid alloy for quantitatively analyzing the consumption of Fe and the formation of Fe-Al compounds. The results indicated that the addition of trace Ti or La could suppress the mutual diffusion. We also observed the microstructures of the Fe-Al intermetallic multilayers and the distribution of Ti or La in the multilayers. A new quaternary phase was identified. The inhibitory effects of Ti and La were also explained by calculating the diffusion barrier energies with density functional theory.