The measurements of contact angle between molten aluminum and MgAl2O4 spinel substrate and surface tension of molten aluminum, and the direct observation of aluminum surface were conducted. An oxide layer, which was formed in the whole surface of molten aluminum during elevating temperature, disappeared almost within about 2 ks at 1273 K. It is guessed that the layer consists of spinel oxide. An increase of surface tension and a decrease of contact angle were caused by elimination of the oxide layer. The marangoni flow, which probably resulted from the difference of surface tension, was observed from upper to lower part of aluminum surface.
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