The Effect of Surface Active Elements on the Wetting Behavior of Iron by Molten Aluminum Alloy

Abstract

Measurements of the contact angle of molten aluminum alloys (Al-Mg, Al-Cu and Al-Si alloys) on solid iron substrate have been carried out aiming at developing a filler sheet for a welding between iron and aluminum. The wettability was estimated by a sessile drop method. The contact angle of molten aluminum drop was measured at 773 and 893 K. Magnesium alloying decreases the contact angle of molten aluminum drop because an evaporation of magnesium prevents a formation of a thin oxide layer at the surface of the molten drop. Since the vapor pressures of these elements at an experimental temperature are much lower than that of magnesium, neither silicon nor copper alloying contributes to improving a wettability on a given experimental condition (T=893 K, P=1.33×10^-3 Pa). A minute quantity of surface active elements such as bismuth, lead and lithium was added with a view to decreasing the surface tension of molten aluminum alloys. A 0.05 mass% addition of bismuth decreases the contact angle most effectively. An excessive addition, however, results in increasing the contact angle. The effect of bismuth addition is more significant at lower temperatures than at higher temperatures.