Study on the formation of intermetallic phases in the new type of Zn-Mg coatings on steel sheets

摘要

Zn-Mg alloy coatings were obtained by physical vapor deposition (PVD) on electroplated steel sheets.Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction (XRD),scanning electron microscope (SEM) and glow discharge optical emission spectrometry (GDOES).It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment.The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics,but also by kinetics.MgZn2 has different morphologies,such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature.Obvious diffusion of Mg starts at 350 ℃,and the diffusion of iron increases significantly when the temperature is elevated to 380 ℃.