浸锌条件对铝合金浸锌层显微组织的影响

Effect of Process Conditions on the Microstructure of the Immersion Zinc Layer on Aluminium Alloys

利用扫描电镜研究了浸锌条件对铝合金浸锌层微观形貌的影响,结果表明,随浸锌时间的增加,锌晶粒不断成核并生长,晶粒尺寸及致密度逐渐增加,晶粒之间彼此相互联结,二次浸锌比一次浸锌所得锌晶粒细小、致密、均匀;随浸锌温度的升高,锌晶粒形状由粒状变为片状,并出现脱落,最适宜的浸锌温度为20～30℃;低浓度无氰多元浸锌溶液所得浸锌层优于传统浓浸锌溶液、稀浸锌溶液、稀浸锌-镍合金溶液;铝合金镀前预处理对浸锌层微观形貌影响也较大。

The effects of process conditions on the microstructure of the immersion zinc layer on A356 alloy has been investigated by scanning electronic microscope. With the increasing of the immersion time, the zinc grain size and the density increase gradually, and the zinc grains adhere each other. The zinc grain obtained in the double-dipping process is finer, compacter and more homogeneous than that obtained in the single-dipping process. With the increasing of the immersion temperature, the morphology of zinc grains changes from spherical shape to flake-like shape. However, higher immersion temperature results in the zinc layer flaking off from the matrix. The optimized immersion temperature is 20 - 30℃. The quality of the zinc layer obtained in a low concentration, and multi-element immersion zinc plating solutions is much better than those obtained in traditional high concentration solution, dilute solution or a dilute solution containing nickel. The pre-treatment also have significant influence on the morphology of the zinc laver.