Solidification experiments of Al-Al3Ni and Al-Bi alloys were carried out in space on board a Chinese recoverable satellite. An obvious double vortical radiant structure of Al-Al3Ni eutectic and a homogeneous microstructure of Al-Bi monotectic were obtained. Combined fluid physics and metallography, the effect of surface tension gradient driven convection on the formation of radiant eutectic structure and the Marangoni migration of second-phase droplets in the molten alloy were analyzed. (C) 1999 COSPAR. Published by Elsevier Science Ltd.