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the melting of small-sized particles during partial remelting, the resulting primary particle size is slightly larger than the initial grain size. But for the alloys having grains larger than ~150 µm, the former size is always smaller than the latter size because of the separation of one original dendrite into two or more primary particles.


The microstructure inhomogeneity of semisolid rod is en- hanced as the rod diameter increases. To obtain a semisolid ingot with uniform microstructure, a cast ingot with uniform as-cast microstructure should be used.


Acknowledgements


This work was supported by the National Basic Research Program of China (Grant No. G2007CB613706), the Devel- opment Program for Outstanding Young Teachers in Lan- zhou University of Technology and the Opening Foundation of Key Laboratory of Gansu Advanced Non-ferrous Metal Materials.


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International Journal of Metalcasting/Winter 2012


Figure 12. Grain sizes in as-microstructures and primary particle sizes in semisolid microstructures of the rods with different diameters.


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