Effect of Mg and Si contents on hot-dip 55Al-Zn plating: Experimental and molecular dynamics simulation

This paper combines experiments and molecular dynamics simulations to investigate the effects and mechanisms of different Mg and Si contents in hot-dip 55Al-Zn plating on the microstructure. Non-equilibrium molecular dynamics was used to simulate the diffusion process between plating and substrate. The structure and composition of the plated layers were analyzed by electron probe and transmission. Both experimental and simulation results show that Mg and Si elements tend to be enriched at the substrate interface and form the Mg2Si phase. The Fe-Al intermetallic compound layer can be divided into two parts, Fe4Al13(Si, Zn), which is far from the substrate, and Fe4Al13, which is close to the substrate, and grows along the direction perpendicular to the substrate interface. When the Mg content in the plating is 0, Si is enriched near the substrate and exists in the form of Si particles. When the Mg content in the plating is high, Si is present mainly in two forms: diffused in the Fe-Al intermetallic compound layer and formation of Mg2Si. The increase of Mg content in the plating promotes the breaking of Fe atomic bonds, but the aggregation of Mg elements hinders the diffusion of Fe. The Si dispersed in the intermetallic compound layer hinders the diffusion of Fe atoms and makes the intermetallic compound layer thinner. The above results explore the microscopic mechanism of the effect of Mg and Si elements on the plating layer at the atomic level and provide new ideas for the study of conventional hot-dip galvanized steel.