| The purpose of this study was to evaluate the microstructure evolution during partial remelting as a function of isothermal holding temperature and time in the semisolid state. SiC particle reinforced magnesium composites were manufactured by Rotation-Cylinder method(RCM) and fully solidified as the billet, and then the microstructure evolutions of them were evaluated through simple reheating procedure. The results showed that the presence of SiC particles led to the fine solid globules compared to those of unreinforced magnesium alloys, and the finer solid globules were achieved with increasing SiC particle fraction. Coalescence was reduced since the solid globules were more isolated with respect to each other by the presence of the particle in grainboundary regions, and Ostwald ripening was also altered by the reduction of the effective diffusion coefficient in the liquid. The average diameters of the solid globules were independent of holding temperature but the standard deviation of the average diameters and the number of the solid globules per area were reduced as temperature increased, mainly due to high liquid fraction. Based on the previous results, it might be suggested that thixoforming of the particle reinforced composites should be performed after short isothermal holding at a relatively high temperature. |
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