Samples of the cross section microstructures of galvannealed steel sheets that lack alloying were analyzed. X-ray diffraction （XRD） tests were carried out. The study discovers that the deficit of alloying was higher...Samples of the cross section microstructures of galvannealed steel sheets that lack alloying were analyzed. X-ray diffraction （XRD） tests were carried out. The study discovers that the deficit of alloying was higher on both sides of the steel sheet when compared to the center and the thickness of the coating on the sides was also higher than the center. The results of the XRD tests demonstrate that the microstructure of the coating with a lack of alloy is mainly composed of zinc,ζ and δ. They also indicate that the lack of alloying is mainly due to a lower galvannealing temperature and thicker coating. It is shown by the optical micrographs of coating that the δ phase forms first in a discontinuous manner at the interface and then rapidly pushes towards the coating and enlarges.展开更多
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 ...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℃.展开更多
文摘Samples of the cross section microstructures of galvannealed steel sheets that lack alloying were analyzed. X-ray diffraction （XRD） tests were carried out. The study discovers that the deficit of alloying was higher on both sides of the steel sheet when compared to the center and the thickness of the coating on the sides was also higher than the center. The results of the XRD tests demonstrate that the microstructure of the coating with a lack of alloy is mainly composed of zinc,ζ and δ. They also indicate that the lack of alloying is mainly due to a lower galvannealing temperature and thicker coating. It is shown by the optical micrographs of coating that the δ phase forms first in a discontinuous manner at the interface and then rapidly pushes towards the coating and enlarges.
文摘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℃.
