In the process of hot-dip Zn-Al-Mg alloy coating,the plating solution dissipates heat in the direction perpendicular to the steel plate,which is considered to be a process of directional solidification.To understand t...In the process of hot-dip Zn-Al-Mg alloy coating,the plating solution dissipates heat in the direction perpendicular to the steel plate,which is considered to be a process of directional solidification.To understand the relationship between microstructure and cooling rate of Zn-Al-Mg alloys,both the phase constitution and microstructure characteristic length scales of Zn-9.5Al-3Mg-0.01Ce(wt.%)alloy were investigated by the directional solidification experiments at different growth velocities(V=40,80,160,250μm·s^(-1)).The experimental results show that the microstructure of directionally solidified Zn-9.5Al-3Mg-0.01Ce alloy is composed of primary Al dendrites and(Zn-Al-Mg2Zn11)ternary eutectics at the growth velocities ranging from 40 to 250μm·s^(-1).The primary Al dendrites are aligned regularly along the growth direction,accompanied with obvious secondary dendrites.The relationship between the microstructure length scale and the thermal parameters of solidification is obtained:λ1=374.66V-0.383,andλ2=167.5V-0.563(λ1is the primary dendrite arm spacing,andλ2 is the secondary dendrit arm spacing).In addition,through the interface response function(IRF)and the nucleation and constitutional undercooling(NCU),the phase selection of Zn-9.5Al-3Mg-0.01Ce is obtained:(Zn+Al+Mg2Zn11)ternary eutectics in the Zn-9.5Al-3Mg-0.01Ce alloy will be replaced by ternary eutectics(Zn+Al+MgZn2)when the growth rate is lower than 7.53μm·s^(-1).展开更多
Based on the advanced integrated technology of materials preparation and formation, a new pattern Zn-Al-Mg-RE anti-corrosion coating for steel structure sustainable design was manufactured by cored wires and high velo...Based on the advanced integrated technology of materials preparation and formation, a new pattern Zn-Al-Mg-RE anti-corrosion coating for steel structure sustainable design was manufactured by cored wires and high velocity arc spraying (HVAS) technologies. The developments of thermally sprayed coatings for steel structure protection were described. Based on Al, Zn, Zn-Al and Zn-Al-Mg coatings, the anti-corrosion properties of new-pattern Zn-Al-Mg-RE coating were evaluated through electrochemical methods including electrochemical polarization and electrochemical impedance spectroscopy (EIS) coupled with SEM and XRD. The models of Zn-Al-Mg-RE coating undergoing corrosion with the initial pinhole defect and the latter with accelerated products were also discussed. The results show that Zn-Al-Mg-RE coating exhibites excellent corrosion resistance for long-term immersion, which is helpful for the sustainable design of steel structure in aggressive corrosion conditions. And the corrosion products seem to possess certain self-sealing function.展开更多
The solidification and corrosion behavior of the Ti/B added Zn-Al-Mg alloys were experimentally investigated by means of microstructure characterization and electrochemical test.The basic calculations were carried out...The solidification and corrosion behavior of the Ti/B added Zn-Al-Mg alloys were experimentally investigated by means of microstructure characterization and electrochemical test.The basic calculations were carried out to predict the characteristics of the Ti-added Zn-Al-Mg alloys.The Zn-Al-Mg ingots with minor doping of Ti/B were prepared and solidified under different cooling rate,including air cooling,water quenching and furnace cooling.The scanning electron microscopy(SEM)and the X-ray diffraction method(XRD)were used to determine the microstructures and phase types of the alloy samples.It could be discovered that trace TiAl3 particles were dispersed in the Ti/B added alloy samples which provide the heterogeneous nucleation sites to refine the size of the dendrites and the eutectic microstructures.More fined microstructures with the addition of both Ti and B were obtained compared with those with the merely addition of Ti,and the water cooled alloys presented the finest microstructures due to the fastest cooling rate.It could also be noticed that with the increasing solidification rate,the percentage of the MgZn_(2) phase turned out to be higher because of the Mg_(2)Zn_(11)↔MgZn_(2) transition,which is in consistent with the results in the actual hot-dip galvanizing process.Electrochemical experiments in the previous work included methods the of the Tafel polarization test and the electrochemical impedance spectroscopy test(EIS).Results show that the quenched Zn-Al-Mg alloy with the addition of both Ti and B takes on best corrosion resistance.Consequently,the addition of certain amount of Ti/B elements and the appropriate elevation of the cooling rate will be the practicable approaches to optimize the microstructure and the corrosion resistance of the Zn-Al-Mg coatings in the actual galvanizing process.展开更多
基金funded by the Key Science and Technology Projects of Gansu Province(Grant No.22ZD6GB019)the fund of the State Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP202204)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2022-ey15)。
文摘In the process of hot-dip Zn-Al-Mg alloy coating,the plating solution dissipates heat in the direction perpendicular to the steel plate,which is considered to be a process of directional solidification.To understand the relationship between microstructure and cooling rate of Zn-Al-Mg alloys,both the phase constitution and microstructure characteristic length scales of Zn-9.5Al-3Mg-0.01Ce(wt.%)alloy were investigated by the directional solidification experiments at different growth velocities(V=40,80,160,250μm·s^(-1)).The experimental results show that the microstructure of directionally solidified Zn-9.5Al-3Mg-0.01Ce alloy is composed of primary Al dendrites and(Zn-Al-Mg2Zn11)ternary eutectics at the growth velocities ranging from 40 to 250μm·s^(-1).The primary Al dendrites are aligned regularly along the growth direction,accompanied with obvious secondary dendrites.The relationship between the microstructure length scale and the thermal parameters of solidification is obtained:λ1=374.66V-0.383,andλ2=167.5V-0.563(λ1is the primary dendrite arm spacing,andλ2 is the secondary dendrit arm spacing).In addition,through the interface response function(IRF)and the nucleation and constitutional undercooling(NCU),the phase selection of Zn-9.5Al-3Mg-0.01Ce is obtained:(Zn+Al+Mg2Zn11)ternary eutectics in the Zn-9.5Al-3Mg-0.01Ce alloy will be replaced by ternary eutectics(Zn+Al+MgZn2)when the growth rate is lower than 7.53μm·s^(-1).
文摘Based on the advanced integrated technology of materials preparation and formation, a new pattern Zn-Al-Mg-RE anti-corrosion coating for steel structure sustainable design was manufactured by cored wires and high velocity arc spraying (HVAS) technologies. The developments of thermally sprayed coatings for steel structure protection were described. Based on Al, Zn, Zn-Al and Zn-Al-Mg coatings, the anti-corrosion properties of new-pattern Zn-Al-Mg-RE coating were evaluated through electrochemical methods including electrochemical polarization and electrochemical impedance spectroscopy (EIS) coupled with SEM and XRD. The models of Zn-Al-Mg-RE coating undergoing corrosion with the initial pinhole defect and the latter with accelerated products were also discussed. The results show that Zn-Al-Mg-RE coating exhibites excellent corrosion resistance for long-term immersion, which is helpful for the sustainable design of steel structure in aggressive corrosion conditions. And the corrosion products seem to possess certain self-sealing function.
基金Funded by the Provincial Key Research and Development Program of Hebei(No.20311004D)the Foundation of Shougang Research Institute of Technology(No.2020RZ06-031)。
文摘The solidification and corrosion behavior of the Ti/B added Zn-Al-Mg alloys were experimentally investigated by means of microstructure characterization and electrochemical test.The basic calculations were carried out to predict the characteristics of the Ti-added Zn-Al-Mg alloys.The Zn-Al-Mg ingots with minor doping of Ti/B were prepared and solidified under different cooling rate,including air cooling,water quenching and furnace cooling.The scanning electron microscopy(SEM)and the X-ray diffraction method(XRD)were used to determine the microstructures and phase types of the alloy samples.It could be discovered that trace TiAl3 particles were dispersed in the Ti/B added alloy samples which provide the heterogeneous nucleation sites to refine the size of the dendrites and the eutectic microstructures.More fined microstructures with the addition of both Ti and B were obtained compared with those with the merely addition of Ti,and the water cooled alloys presented the finest microstructures due to the fastest cooling rate.It could also be noticed that with the increasing solidification rate,the percentage of the MgZn_(2) phase turned out to be higher because of the Mg_(2)Zn_(11)↔MgZn_(2) transition,which is in consistent with the results in the actual hot-dip galvanizing process.Electrochemical experiments in the previous work included methods the of the Tafel polarization test and the electrochemical impedance spectroscopy test(EIS).Results show that the quenched Zn-Al-Mg alloy with the addition of both Ti and B takes on best corrosion resistance.Consequently,the addition of certain amount of Ti/B elements and the appropriate elevation of the cooling rate will be the practicable approaches to optimize the microstructure and the corrosion resistance of the Zn-Al-Mg coatings in the actual galvanizing process.
