Effect of cooling rate on microstructure and corrosion resistance of Al-Zn-Mg-Si coating
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维普
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热浸镀Al-Zn-Mg-Si镀层钢板具有优异耐蚀性,已被广泛应用于建筑、家电和汽车等领域.为探究冷却速率对镀层组织的影响,利用热镀锌模拟器制备了 Al-Zn-Mg-Si镀层钢板试样,镀层成分为55Al-42Zn-1.5Mg-1.5Si,利用光学显微镜、扫面电镜、X射线能谱仪和盐雾试验研究了不同冷却速率下镀层的微观组织及耐蚀性.结果表明:当冷却速率从10 ℃/s提高到22 ℃/s时,Al-Zn-Mg-Si镀层组织和性能发生显著变化,枝晶和枝晶间距明显细化,晶花尺寸缩小78％,枝晶与枝晶间隙过渡区的宽度增大95％,多数富Zn相从大块状变化为短棒状,在枝晶间隙中弥散分布,枝晶取向的多样性使镀层宏观表面更加均匀;提高冷却速度率有利于减缓镀层腐蚀蔓延速度,与冷却速率10 ℃/s相比,冷却速率22 ℃/s下的耐蚀性延长时间大于2 496 h.
Hot-dip Al-Zn-Mg-Si coated steel plates possess excellent corrosion resistance and have been widely applied in the fields of construction,home appliances,and automobiles.To investigate the influence of cooling rate on the coating microstructure,hot-dip galvanizing simulators were used to prepare Al-Zn-Mg-Si coated steel plate samples with a coating composition of 55A1-42Zn-1.5Mg-1.5Si.OM,SEM,EDS,and salt spray tests were employed to study the microstructure and corrosion resistance of the coatings under different cooling rates.The results showed that when the cooling rate increased from 10 ℃/s to 22 ℃/s,sig-nificant changes occurred in the microstructure and properties of the Al-Zn-Mg-Si coating.The dendrites and dendrite spacing were significantly refined,the size of spangles was reduced by 78％and the width of the transition zone between dendrites and dendrite gaps was increased by 95％.Most Zn-rich phases changed from large blocks to short rods,and the diversity of dendrite orientations distributed in the dendrite gaps made the macroscopic surface of the coating appear more uniform.Increasing the cooling rate was beneficial to slowing down the corrosion spreading rate of the coating.Compared with a cooling rate of 10 ℃/s,the corrosion resistance duration at a cooling rate of 22 ℃/s was extended by more than 2 496 h.
Al-Zn-Mg-Si coatingcooling ratespanglemicrostructure of the coatingcorrosion resistance
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