Papers by Author: M.H. Kim

Abstract: Microstructural variation is quantitatively characterized by measured undercooling. For neareutectic Al-13wt%Si alloys, microstructure transitions, which include a phase change from eutectic to primary α-Al dendrite plus eutectic and a morphological change from α-Al dendrite to equiaxed Al grains, were observed with increasing undercooling levels. For hypereutectic Al-Si alloys, microstructure transitions, which include a morphological change of primary and eutectic Si crystals, were also obtained quantitatively by increasing undercooling.

Abstract: This paper investigates the effect of bubble on the primary Si size in Al-18wt.%Si alloy. The primary Si size observed was varied with bubble size and bubbling time in bubble process. The effect of the holding temperature of the melt in bubbling process was also investigated. In water model, as the injecting bubble size decreases, the residual bubble size in the water decreases and the residual bubble conservation time in the water increases. Also in the experiment of Al melt, the primary Si size decreases, as the injecting bubble size decreases and as the bubble processing time increases. Pore was observed at the center of primary Si. This pore was observed at many Si phases. So, this experiment suggests that the bubble can be used as nucleation sites of primary Si.