Seong-Ho Ha

Effect of Mg Contents on Fluidity of Al-xMg Alloys

This study is focused on a basic approach for the fluidity of the Al-Mg binary system. The objective of this study is to investigate the fluidity change of the Al-Mg alloys with increasing Mg content. As a result of fluidity test, pure Al showed the highest value in all the examined alloys. With 2.5%Mg addition, it decreased rapidly. On the other hand, the gain of the flow length was shown with increasing Mg content from 5%Mg addition. The change of the fluidity shown in this study is roughly similar to that reported previously. However, they also showed the difference in the Mg content which has the most viscous fluidity. It is considered that it is attributed to the different experimental conditions. In microstructures, with increasing the Mg content, the dendritic α-Al was developed and the existence of precipitation regarded as β-phase (Mg5Al8) is shown in the grain boundary. This tendency became conspicuous from the 5wt%Mg addition. And then, the grains were refined with the formation of the precipitation.

Fluidity of A356 Alloy during In-Ladle DTC Rheocasting

There are two primary semisolid processing (S2P) routes, thixocasting and rheocasting. Especially, the rheocasting process has become a new focus in the field of semisolid process because of its many advantages such as increased shot size flexibility, no special SSM billet, inhouse recycling of scrap and smaller investment, compared with the thixoforming process. In-Ladle direct thermal control (DTC) rheocasting was developed, based on the fact that there is slurry and mush transition in molten metal, which is controlled by solid shape and relative interfacial energy. Fluidity is investigated by applying pressure casting for optimizing conditions of in-ladle DTC rheocasting of A356 Al alloy based on research results of simulation and actual microstructure control.