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

Abstract

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.

Keywords

• aluminum alloy
• hot dipping
• numerical simulation
• ultrasonic cavitation