Microstructure and rheological behavior of hypereutectic semi-solid Al-Si alloy under low shear rates compression test

Permanent mold cast cylindrical samples were reprocessed to form semi-solid billets of A390 Al-Si alloy, employing a thixocasting method. The billets were reheated to predetermined mushy zone temperatures and held isothermally during parallel plate compression tests. The deformation behavior of the billets was measured at different applied pressures, and fraction solids determined by the preheating temperature. The calculated viscosities confirmed pseudoplastic behavior of the semi-solid alloys and were correlated to the solid fraction and shear rate to illustrate the effect of metallurgical and process parameters on the viscosity and the consequent rheological behavior of these alloys.