| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 97 === Currently, the rheocasting equipment for composite materials, in general, is less mobility and needs longer time to prepare the pre-processed raw material. Moreover, there still acquire additional devices. In order to overcome these drawbacks existed in current rheocasting processes, the change of runner design might be considered. As liquid metal with added powders flowed through a runner with reduction in the cross-section area, the powders could be dispersed uniformly within the melt by virtue of influence of shear force. In addition, the dendritic structure could be cut off by the shear force and led to a spherical form.
The numerical simulation was used in this paper to study the effect of runner-reduction ratio on the dispersing uniformity of added powders inside alloy melt. The parameters studied were runner shape, gating system type and reduction ratio in cross section area. There were two runner shapes, two gating system and six reduction ratios, respectively, used in this study, such as straight and S-type, and tangent gating system and tangent runner fan-shaped gating system, and 0%, 20%, 30%, 40%, 50%, and 60%. The results revealed that the tangent gating system can dispersing uniformity of powders by swirl flow, but that can air entrapment easy; dispersing uniformity of powders for tangent runner fan-shaped gating system with straight type was better than that for S-type. The best dispersing uniformity was achieved when the reduction ratio was up to 60%.
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