基于非线性超声空化效应的铝合金热浸镀工艺

Hot dip process of aluminum alloy based on nonlinear ultrasonic cavitation effect

在390℃热浸镀锌过程中施加20 kHz的超声波,采用数值分析法求解Keller-Miksis和Mettin方程,描述ZnAl8熔池中0~800 W超声空泡的生长规律和空化效应,研究超声功率对镀层ZnAl8合金组织的影响,以及对1050铝合金表面氧化膜的作用。结果表明:空化效应与超声功率呈现出非线性的变化规律,当超声功率为0~500 W时,空化以稳态效应为主,空化能量不足以消除镀层合金初生相的粗大枝晶组织,也不能消除铝合金氧化膜。当功率为600~800 W时,空化以瞬态崩溃破裂的方式释放能量,其中700~800 W的空化压强和温度效应可以将铝合金表面氧化膜击碎和熔蚀,为镀层中元素扩散提供了铺展润湿和物质传输的通道,镀层ZnAl8合金与1050铝合金基体之间形成了良好的冶金结合,镀层合金呈细小均匀的蔷薇组织。

20 kHz ultrasounds were applied in the process of 390℃hot dip galvanization of 1050 aluminum alloy.The evolution of the cavitation bubbles were solved numerically from the Keller-Miksis and Mettin equations.The growth of the cavitation bubbles of 0-800 W ultrasonic cavitation and their effects in the ZnAl8 molten pool were described.The effects of the ultrasonic power on the alloy structure of the coating and the removal of the oxide film on the surface of the 1050 aluminum alloy were analyzed.The results show that cavitational effects display nonlinear relation with the ultrasonic power.For ultrasonic power in the range of 0-500 W,stable cavitation dominates.The dendritic structure of the coating ZnAl8 alloy and the aluminium oxide film remain mostly unchanged.When the power is 600-800 W,transient cavitation bubbles release energy in the form of violent collapse.The high cavitation pressure and temperature,respectively,crush and melt the oxide film on the surface of the aluminum alloy,which facilitates spreading,wetting and transfer of the elements between the aluminum substrate and the coating.Therefore,under the action of power ultrasonic waves of 700-800 W,good metallurgical bond is formed between the coating alloy and the aluminum alloy substrate,and the coating alloy displays fine and uniform rosette-like microstructure.